Immunohistochemistry in Diagnostic Parathyroid Pathology

Diagnostic and Therapeutic Challenges in Parathyroid Cancers: 15 Years' Experience in a Tertiary Center and an Endocrine Surgery Referral Hospital

Background: Parathyroid cancers are rare endocrine malignancies that pose diagnostic and therapeutic challenges, particularly when discovered incidentally or in the presence of multiple endocrine disorders. This study aims to provide clinical, biochemical and pathological insights into these malignancies through a retrospective case series. Methods: We analyzed retrospectively, from a tertiary and an endocrine surgery referral center, 13 cases of parathyroid cancers, where 4 cases were associated with thyroid cancers, including demographic data, clinical presentation, biochemical markers, imaging, surgical interventions, histopathological findings and follow-up outcomes. Descriptive statistics were used to summarize patient characteristics. Results: The median age of the cohort was 64 (range: 40-81 years), with a female-to-male ratio of 8:5. More than half of the cases (61.53%) were diagnosed incidentally, with common biochemical findings including elevated parathyroid hormone (PTH) levels (median: 430 pg/mL) and hypercalcemia in 80% of the patients. All patients underwent surgery, with parathyroid resections with concomitant total thyroidectomy (62%) or lobectomy (23%) as the most common interventions. Histopathological analysis confirmed parathyroid carcinoma in all cases, with coexisting thyroid malignancies observed in 31%. An immunohistochemical profile performed in about half of the patients was in accordance with previously published data. Postoperative normalization of PTH levels was achieved in 77% of patients, and no recurrence or metastasis was observed in 85% of cases during follow-up. Conclusions: Despite the exceptional rarity of the disease, this case series highlights the importance of preoperative biochemical and imaging evaluation and the efficacy of surgical management. Long-term outcomes remain favorable with early diagnosis and diligent postoperative monitoring. Further research into molecular biomarkers and targeted therapies is warranted to improve the management of advanced or recurrent disease.

The Molecular Classification of Pheochromocytomas and Paragangliomas: Discovering the Genomic and Immune Landscape of Metastatic Disease

Pheochromocytomas (PCCs) and paragangliomas (PGLs, together PPGLs) are the most hereditary tumors known. PPGLs were considered benign, but the fourth edition of the World Health Organisation (WHO) classification redefined all PPGLs as malignant neoplasms with variable metastatic potential. The metastatic rate differs based on histopathology, genetic background, size, and location of the tumor. The challenge in predicting metastatic disease lies in the absence of a clear genotype-phenotype correlation among the more than 20 identified genetic driver variants. Recent advances in molecular clustering based on underlying genetic alterations have paved the way for improved cluster-specific personalized treatments. However, despite some clusters demonstrating a higher propensity for metastatic disease, cluster-specific therapies have not yet been widely adopted in clinical practice. Comprehensive genomic profiling and transcriptomic analyses of large PPGL cohorts have identified potential new biomarkers that may influence metastatic potential. It appears that no single biomarker alone can reliably predict metastatic risk; instead, a combination of these biomarkers may be necessary to develop an effective prediction model for metastatic disease. This review evaluates current guidelines and recent genomic and transcriptomic findings, with the aim of accurately identifying novel biomarkers that could contribute to a predictive model for mPPGLs, thereby enhancing patient care and outcomes.

Diagnosis and Management of Parathyroid Carcinoma

Parathyroid carcinoma (PC) is a rare malignancy, often characterized by the unregulated secretion of parathyroid hormone. The sequelae of severe hypercalcemia together with direct complications from tumor dissemination in patients with advanced disease are usually fatal. Due to its rarity, formal studies to guide the diagnosis and management of parathyroid carcinoma are lacking. However, recent data from case reports, case series, and registry studies suggest the emergence of new and effective treatment approaches for this understudied disease. We reviewed existing literature on the diagnosis and management of parathyroid carcinoma. Our findings suggest that traditional approaches such as surgical resection for both localized and metastatic diseases continue to play an important role in patient management. For patients with unresectable disease, newer systemic treatment approaches, including the use of temozolomide and tyrosine kinase inhibitors, may offer clinical benefit.

Neuroendocrine neoplasms of head and neck, genitourinary and gynaecological systems, unknown primaries, parathyroid carcinomas and intrathyroid thymic neoplasms: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up

•This Clinical Practice Guideline provides key recommendations for managing rare endocrine tumours. •Neuroendocrine neoplasms of different origins, parathyroid carcinoma and intrathyroid thymic neoplasms are included. •The guideline covers clinical imaging and pathological diagnosis, staging and risk assessment, treatment and follow-up. •The authors comprise a multidisciplinary group of experts from different institutions and countries in Europe. •Recommendations are based on available scientific data and the authors’ collective expert opinion.

Syndromic MEN1 parathyroid adenomas consist of both subclonal nodules and clonally independent tumors

Primary hyperparathyroidism with parathyroid tumors is a typical manifestation of Multiple Endocrine Neoplasia Type 1 (MEN1) and is historically termed "primary hyperplasia". Whether these tumors represent a multi-glandular clonal disease or hyperplasia has not been robustly proven so far. Loss of Menin protein expression is associated with inactivation of both alleles and a good surrogate for a MEN1 gene mutation. The cyclin-dependent kinase inhibitor 1B (CDKN1B) gene is mutated in MEN4 and encodes for protein p27 whose expression is poorly studied in the syndromic MEN1 setting.Here, we analyzed histomorphology and protein expression of Menin and p27 in parathyroid adenomas of 25 patients of two independent, well-characterized MEN1 cohorts. The pattern of loss of heterozygosity (LOH) was assessed by fluorescence in situ hybridization (FISH) in one MEN1-associated parathyroid adenoma. Further, next-generation sequencing (NGS) was performed on eleven nodules of four MEN1 patients.Morphologically, the majority of MEN1 adenomas consisted of multiple distinct nodules, in which Menin expression was mostly lost and p27 protein expression reduced. FISH analysis revealed that most nodules exhibited MEN1 loss, with or without the loss of centromere 11. NGS demonstrated both subclonal evolution and the existence of clonally unrelated tumors.Syndromic MEN1 parathyroid adenomas therefore consist of multiple clones with subclones, which supports the current concept of the novel WHO classification of parathyroid tumors (2022). p27 expression was lost in a large fraction of MEN1 parathyroids and must therefore be used with caution in suggesting MEN4.

High lymphocyte signature genes expression in parathyroid endocrine cells and its downregulation linked to tumorigenesis

BACKGROUND

To date, because of the difficulty in obtaining normal parathyroid gland samples in human or in animal models, our understanding of this last-discovered organ remains limited.

METHODS

In the present study, we performed a single-cell transcriptome analysis of six normal parathyroid and eight parathyroid adenoma samples using 10 × Genomics platform.

FINDINGS

We have provided a detailed expression atlas of parathyroid endocrine cells. Interestingly, we found an exceptional high expression levels of CD4 and CD226 in parathyroid endocrine cells, which were even higher than those in lymphocytes. This unusual expression of lymphocyte markers in parathyroid endocrine cells was associated with the depletion of CD4 T cells in normal parathyroid glands. Moreover, CD4 and CD226 expression in endocrine cells was significantly decreased in parathyroid adenomas, which was associated with a significant increase in Treg counts. Finally, along the developmental trajectory, we discovered the loss of POMC, ART5, and CES1 expression as the earliest signature of parathyroid hyperplasia.

INTERPRETATION

We propose that the loss of CD4 and CD226 expression in parathyroid endocrine cells, coupled with an elevated number of Treg cells, could be linked to the pathogenesis of parathyroid adenoma. Our data also offer valuable information for understanding the noncanonical function of CD4 molecule.

FUNDING

This work was supported by the National Key R&D Program of China (2022YFA0806100), National Natural Science Foundation of China (82130025, 82270922, 31970636, 32211530422), Shandong Provincial Natural Science Foundation of China (ZR2020ZD14), Innovation Team of Jinan (2021GXRC048) and the Outstanding University Driven by Talents Program and Academic Promotion Program of Shandong First Medical University (2019LJ007).

Insights into Hyperparathyroidism-Jaw Tumour Syndrome: From Endocrine Acumen to the Spectrum of CDC73 Gene and Parafibromin-Deficient Tumours

A total of 1 out of 10 patients with primary hyperparathyroidism (PHP) presents an underlying genetic form, such as multiple endocrine neoplasia types 1, 2A, etc., as well as hyperparathyroidism-jaw tumour syndrome (HJT). We aimed to summarise the recent data, thus raising more awareness regarding HJT, from the clinical perspective of PHP in association with the challenges and pitfalls of CDC73 genetic testing and parafibromin staining. This narrative review included a sample-focused analysis from the past decade according to a PubMed search. We identified 17 original human studies (≥4 patients per article). The mean age at disease onset was between 20.8 and 39.5 years, while the largest study found that 71% of patients had HJT recognised before the age of 30. Males and females seemed to be equally affected, in contrast with sporadic PHP. PHP represented the central manifestation of HJT, occurring as the first manifestation in up to 85% of HJT cases. A biochemistry panel found a mean serum calcium level above the level of 12 mg/dL in PHP. PTH was elevated in HJT as well, with average values of at least 236.6 pg/mL. The most frequent pathological type in PHP was a parathyroid adenoma, but the incidence of a parathyroid carcinoma was much higher than in non-HJT cases (15% of all parathyroid tumours), with the diagnosis being established between the age of 15 and 37.5. In some families up to 85% of carriers suffered from a parathyroid carcinoma thus indicating that certain CDC73 pathogenic variants may harbour a higher risk. An important issue in HJT was represented by the parafibromin profile in the parathyroid tumours since in HJT both parathyroid adenomas and carcinomas might display a deficient immunoreactivity. Another frequent manifestation in HJT was ossifying fibromas of the jaw (affecting 5.4% to 50% of patients; the largest study found a prevalence of 15.4%). HJT was associated with a wide variety of kidney lesion (mostly: kidney cysts, with a prevalence of up to 75%, and renal tumours involved in 19% of patients). The risk of uterine lesions seemed increased in HJT, especially with concern to leiomyomas, adenofibromas, and adenomyosis. The underlying pathogenic mechanisms and the involvement of CDC73 pathogenic variants and parafibromin expression are yet to be explored. Currently, the heterogeneous expression of parafibromin status and, the wide spectrum of CDC73 mutations including the variety of clinical presentations in HJT, make it difficult to predict the phenotype based on the genotype. The central role of HJT-PHP is, however, the main clinical element, while the elevated risk of parathyroid carcinoma requires a special awareness.

Molecular pathology of endocrine gland tumors: genetic alterations and clinicopathologic relevance

Tumors of the endocrine glands are common. Knowledge of their molecular pathology has greatly advanced in the recent past. This review covers the main molecular alterations of tumors of the anterior pituitary, thyroid and parathyroid glands, adrenal cortex, and adrenal medulla and paraganglia. All endocrine gland tumors enjoy a robust correlation between genotype and phenotype. High-throughput molecular analysis demonstrates that endocrine gland tumors can be grouped into molecular groups that are relevant from both pathologic and clinical point of views. In this review, genetic alterations have been discussed and tabulated with respect to their molecular pathogenetic role and clinicopathologic implications, addressing the use of molecular biomarkers for the purpose of diagnosis and prognosis and predicting response to molecular therapy. Hereditary conditions that play a key role in determining predisposition to many types of endocrine tumors are also discussed.

[The role of immunohistochemical examination in the differential diagnosis of atypical tumors and carcinomas of parathyroid glands]

Differential diagnosis of atypical parathyroid tumors (APT) and parathyroid carcinomas (PC) is important in determining further management and prognosis. Morphologic diagnosis is sometimes difficult, in which case it is supplemented by immunohistochemical (IHC) examination.

OBJECTIVE

Studying the role of IHC analysis in the differential diagnosis of APT and PC.

MATERIAL AND METHODS

The study included 44 patients with morphologic diagnosis of the APT established after surgical treatment for primary hyperparathyroidism on the basis of Endocrinology Research Centre during 2018-2023. All cases underwent IHC examination with evaluation of CD31/CD34 and parathormone (PTH) expression for identification of vascular invasion, Ki-67, parafibromin.

RESULTS

According to the results of IHC analysis in 8/44 patients (18.2%) the diagnosis of APT was revised in favor of the PC: in 7 of them vascular invasion was detected; in 1 patient the additional series of slices in the surrounding fatty tissue revealed foci of tumor growth, confirmed by positive reaction with antibodies to PTH. According to IHC results, the material was divided into 2 groups: APT and PC. There were no differences in clinical and morphological characteristics, Ki-67% level and parafibromin expression between the groups.

CONCLUSION

Assessment of clinical and laboratory-instrumental data at the preoperative stage does not allow differentiating APT from PC. In case of APT diagnosis and detection of suspicious morphological features, it is necessary to perform IHC examination to exclude PC.

Some uncommon cystic lesions in the anterior head and neck region: Pitfalls to be avoided on cytology

Cystic lesions of the anterior head and neck region are a challenging and frequent finding on cytological smears. The scant amount of cellular material in cystic slides poses the greatest difficulty to interpretation, so that frequently they are diagnosed as inadequate or with minimal cellular component. Despite the majority of cystic lesions being benign, a minor portion consist of malignant cystic entities. In these latter cases, the evidence of very scant malignant cells can be misdiagnosed and/or underestimated, leading to a false negative diagnosis. Many papers have already described and detailed the range of possible benign and malignant cystic lesions in head and neck. In the current review we have focused on the less common entities that often lead to serious misinterpretation.

Top 10 Clear Cell Head and Neck Lesions to Contemplate

BACKGROUND

Optically clear cytoplasm may occur in neoplastic and non-neoplastic conditions, either as a characteristic feature of a disease entity or as a morphologic rarity, potentially creating diagnostic dilemmas in various organ systems. In the head and neck, clear cell change can occur in lesions of salivary, odontogenic, thyroid, parathyroid, or sinonasal/skull base origin, as well as in metastases to these regions.

METHODS

This review elaborates the top ten clear cell lesions in the head and neck, emphasizing their distinguishing histologic, immunohistochemical, and molecular attributes, and presents a rational approach to arriving at an accurate classification.

RESULTS

Cytoplasmic pallor or clearing may be caused by accumulations of glycogen, lipid, mucin, mucopolysaccharides, water, foreign material, hydropic organelles, or immature zymogen granules. Overlapping morphologic features may present a diagnostic challenge to the surgical pathologist. Similarity in immunohistochemical profiles, often due to common cell type, as well as rare non-neoplastic mimics, furthers the diagnostic conundrum.

CONCLUSIONS

The top ten lesions reviewed in this article are as follows: (1) clear cell carcinoma (salivary and odontogenic), (2) mucoepidermoid carcinoma, (3) myoepithelial and epithelial-myoepithelial carcinoma, (4) oncocytic salivary gland lesions, (5) squamous cell carcinoma, (6) parathyroid water clear cell adenoma, (7) metastatic renal cell carcinoma (especially in comparison to clear cell thyroid neoplasms), (8) sinonasal renal cell-like adenocarcinoma, (9) chordoma, and (10) rhinoscleroma.

Diagnostic, Prognostic, and Predictive Role of Ki67 Proliferative Index in Neuroendocrine and Endocrine Neoplasms: Past, Present, and Future

The introduction of Ki67 immunohistochemistry in the work-up of neuroendocrine neoplasms (NENs) has opened a new approach for their diagnosis and prognostic evaluation. Since the first demonstration of the prognostic role of Ki67 proliferative index in pancreatic NENs in 1996, several studies have been performed to explore its prognostic, diagnostic, and predictive role in other neuroendocrine and endocrine neoplasms. A large amount of information is now available and published results globally indicate that Ki67 proliferative index is useful to this scope, although some differences exist in relation to tumor site and type. In gut and pancreatic NENs, the Ki67 proliferative index has a well-documented and accepted diagnostic and prognostic role and its evaluation is mandatory in their diagnostic work-up. In the lung, the Ki67 index is recommended for the diagnosis of NENs on biopsy specimens, but its diagnostic role in surgical specimens still remains to be officially accepted, although its prognostic role is now well documented. In other organs, such as the pituitary, parathyroid, thyroid (follicular cell-derived neoplasms), and adrenal medulla, the Ki67 index does not play a diagnostic role and its prognostic value still remains a controversial issue. In medullary thyroid carcinoma, the Ki67 labelling index is used to define the tumor grade together with other morphological parameters, while in the adrenal cortical carcinoma, it is useful to select patients to treated with mitotane therapy. In the present review, the most important information on the diagnostic, prognostic, and predictive role of Ki67 proliferative index is presented discussing the current knowledge. In addition, technical issues related to the evaluation of Ki67 proliferative index and the future perspectives of the application of Ki67 immunostaining in endocrine and neuroendocrine neoplasms is discussed.

Preoperative, Intraoperative, and Postoperative Parathyroid Pathology: Clinical Pathologic Collaboration for Optimal Patient Management

Parathyroid disease typically presents with parathyroid hyperfunction as result of neoplasia or a consequence of non-neoplastic systemic disease. Given the parathyroid gland is a hormonally active organ with broad physiologic implications and serologically accessible markers for monitoring, the diagnosis of parathyroid disease is predominantly a clinical pathologic correlation. We provide the current pathological correlates of parathyroid disease and discuss preoperative, intraoperative, and postoperative pathology consultative practice for optimal patient care.

Advances and Updates in Parathyroid Pathology

Hyperparathyroidism is a common endocrine disorder characterized by elevated levels of parathyroid hormone and hypercalcemia and is divided into 3 types: primary, secondary, and tertiary. Distinction between these types is accomplished by correlation of clinical, radiologic, and laboratory findings with pathologic features. Primary hyperparathyroidism occurs sporadically in 85% of cases with the remaining cases associated with multiple familial syndromes. The pathologic manifestations of primary hyperparathyroidism include parathyroid adenoma, parathyroid hyperplasia, and parathyroid carcinoma. Recent advances in the understanding of the pathogenesis of parathyroid disease has helped to refine the diagnosis and classification of parathyroid lesions. The identification of multiple clonal proliferations in traditional multiglandular parathyroid hyperplasia has led to the adoption by the World Health Organization (WHO) of the alternate term of primary hyperparathyroidism-related multiglandular parathyroid disease. Additional nomenclature changes include the adoption of the term atypical parathyroid tumor in lieu of atypical parathyroid adenoma to reflect the uncertain malignant potential of these neoplasms. Clinical and morphologic features characteristic of familial disease have been described that can help the practicing pathologist identify underlying familial disease and provide appropriate management. Use of ancillary immunohistochemistry and molecular studies can be helpful in classifying parathyroid neoplasms. Parafibromin has proven useful as a diagnostic and prognostic marker in atypical parathyroid tumors and parathyroid carcinomas. This review provides an update on the diagnosis and classification of parathyroid lesions considering the recent advances in the understanding of the molecular and clinical features of parathyroid disease and highlights the use of ancillary studies (immunohistochemical, and molecular) to refine the diagnosis of parathyroid lesions.

Large parathyroid adenomas: Potential mechanisms to reconcile adenoma size and disease phenotype

Parathyroid adenomas weighing more than 3.5 g are reported variously as "atypical", "large" or "giant" parathyroid adenomas. All such adenomas are rare variants accounting for no more than 1.5% of all parathyroid adenomas. Large parathyroid adenomas are often associated with more severe form of the disease, including osteitis fibrosa cystica (OFC) and share many biochemical, histological, and molecular features of both benign and malignant parathyroid neoplasms, and are considered a distinct clinical entity. However, the pathogenesis of oversized parathyroid adenomas and the often-associated skeletal phenotype remains unclear. We present 5 cases of primary hyperparathyroidism (PHPT) with OFC, an uncommon manifestation of contemporary PHPT, associated with larger parathyroid adenomas, seen in the Bone and Mineral Disorders Clinic of the Henry Ford Health in the last 30 years to illustrate the critical role of vitamin D nutrition in the pathogenesis of both the OFC and adenoma size. The estimated prevalence of OFC was very low 0.2%, 5 of the >3000 surgically confirmed cases of PHPT seen during this time. The mean ± SD values were: age: 36.8 ± 22.1 years (4 of the 5 <36years), serum calcium 11.6 ± 1.1 mg/dl, alkaline phosphatase 799 ± 487 IU/L, PTH 1440 ± 477 pg/ml, 25-hydroxyvitamin D 13.0 ± 8.9 ng/ml, 1,25-dihyroxyvitamin D 26.5 ± 13.7 pg/ml, urine calcium 562 ± 274 mg/day, and parathyroid adenoma weight 4.53 ± 2.2 g. Parathyroidectomy led to the resolution of both the biochemical indices and OFC in each patient without recurrence over >10 years of follow-up. Because OFC is a very rare in the West, but very common areas of endemic vitamin D deficiency, we also examined the relationship between vitamin D nutrition, as assessed by serum 25-hydroxyvitamin D level, and parathyroid adenoma weight as well as prevalence of OFC in two large secularly diverse cohorts of patients with PHPT (Detroit, USA and Chandigarh, India). Based on this relationship and the relative prevalence of OFC in these two large cohorts, we propose that vitamin D nutrition (and perhaps calcium nutrition) best explains both the adenoma size and prevalence of OFC.

Clinicopathological Profile of Primary Hyperparathyroidism with Special Reference to Ki-67 Labelling Index

CONTEXT

Primary hyperparathyroidism (PHPT) can occur due to a neoplastic process or hyperplasia. While the disease presentation is predominantly asymptomatic in developed countries, this is not the case yet in India. Differentiation of the type of lesion can only be done based on histomorphology but has its own challenges. Immunohistochemical markers like Ki-67 have been studied to aid in diagnosis but data on this is sparse from India.

AIMS

The aim of this study is to assess the clinical, biochemical and pathological profile of PHPT and to analyse the differences in immunohistochemical marker Ki-67 among the various lesions.

SETTING AND DESIGN

A descriptive study was carried out on 38 PHPT patients who were treated at our institute from January 2011 to March 2021.

MATERIALS AND METHODS

Post-surgery, the causative lesions were categorised as adenoma (31), hyperplasia (5) and carcinoma (2). Clinical, biochemical, radiological and histopathological features of all lesions were collected and analysed. Ki-67 proliferation index was calculated. The various parameters were compared across the three groups of lesions and correlated with Ki-67 index.

RESULTS

Out of 38 patients, 37 were symptomatic with skeletal symptoms being the most common followed by renal symptoms. There was no difference in clinical or biochemical parameters among the three types of lesions. Significant negative correlation was seen between serum iPTH and serum 25-OH Vitamin D levels (P0.006) The median Ki-67 index was found to be 0.40% in hyperplasia, 0.49% in adenoma and 5.84% in carcinoma.

CONCLUSION

PHPT still presents as an overtly symptomatic disease in India. Diagnosis of the nature of lesion depends on the accurate application of morphological criteria. A high Ki-67 index was not found to be an absolute marker of carcinoma, as it was also seen in a small proportion of atypical adenomas.

Production of parathyroid-like cells from thyroid stem cells in co-culture environment

BACKGROUND

Parathyroid-like cells were aimed to be developed using cells isolated from thyroid since their embryological origins are the same.

METHOD

Activin A and sonic hedgehog (Shh) are the proteins used in differentiation (dif) medium. Parathyroid and thyroid cells were cultured in a 3-dimensional environment and divided into five groups: thyroid standard (st) medium, thyroid dif medium, parathyroid st medium, thyroid-parathyroid co-culture st medium, and thyroid-parathyroid co-culture dif medium. Throughout 28 days of incubation, groups were investigated by carrying out the live dead assay, confocal microscopy, real-time PCR, immunohistochemistry and biochemical assays.

RESULTS

Thyroid-parathyroid co-culture cells grown in dif medium exhibited upregulated expressions of parathormone (PTH) (5.1-fold), PTH1R (3.6-fold), calcium sensing receptor (CaSR) (8.8-fold), and loss of thyroid-specific thyroid transcription factor 1 (TTF1) expression when compared to the thyroid st medium group. PTH secretion decreased by 35% in the parathyroid st medium group and 99.9% in the thyroid-parathyroid co-culture st medium group but decreased only 3.5% in the thyroid-parathyroid co-culture dif medium group on day 28.

CONCLUSION

Using Activin A and Shh proteins, thyroid stem/progenitor cells were differentiated to parathyroid-like cells successfully in a co-culture environment. A potentially effective novel method for cell differenatiation is co-culture of cells having the same embryological origin.

Analysis of the successful clinical treatment of 140 patients with parathyroid adenoma: A retrospective study

BACKGROUND

Parathyroid adenoma (PA) sometimes recurs after surgery, how to improve the surgical success rate of PA is the key to the treatment of this disease.

AIM

To investigate the clinical features, diagnosis, and surgical treatment of patients with PA.

METHODS

Patients who were pathologically confirmed with PA and had undergone surgery for the first time between January 2010 and December 2017 at the Beijing Shijitan Hospital affiliated to Capital Medical University were included in the study. The clinical features, localization diagnosis, and surgical treatment of these patients were analyzed.

RESULTS

Of the 140 patients, 32 were male and 108 were female; 132 cases had one adenoma, and 8 had two adenomas. In addition, 114 cases had clinical symptoms, among which 51, 28, 23, 8, and 4 had urinary system, skeletal system, digestive system, neuromuscular system, and neuropsychiatric symptoms, respectively, while 26 cases had no obvious symptoms. The median level of preoperative parathyroid hormone (PTH) was 201.0 pg/mL. The positive detection rate of technetium-99m sestamibi (Tc-99m MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT), ultrasound examination, and the combined use of Tc-99m MIBI SPECT/CT and ultrasound examination was 92.9%, 85.5%, and 96.4%, respectively. Open surgery was performed in all patients, and PTH was monitored during surgery. The success rate of surgery was 98.6%. After surgery, 21 cases developed hypocalcemia, 1 case developed temporary hoarseness, and 19 cases had transient hypoparathyroidism but there was no permanent hypoparathyroidism, postoperative hemorrhage, or hematoma in the surgical area.

CONCLUSION

For patients with clinically unexplained skeletal system, urinary system, and neuropsychiatric symptoms, the possibility of PA should be considered. Imaging examinations such as ultrasound and Tc-99m MIBI SPECT/CT could be integrated before surgery to obtain accurate localization diagnosis. Precise preoperative localization, intraoperative PTH monitoring, and delicate surgery to protect the integrity of the PA capsule ensure a minimally invasive and successful surgery.

A Silent Non-thyroidal Adenoma in the Thyroid

The surgeon needs to assess clinically significant thyroid nodules as they may represent aggressive forms of thyroid cancer or ectopic parathyroid glands. We discuss one such unusual nodule in the thyroid.

Head and Neck Cystic Lesions: A Cytology Review of Common and Uncommon Entities

BACKGROUND

Cystic lesions of the head and neck are a diagnostic challenge since they are seen in the clinical presentation of a wide variety of conditions. Herein, common and uncommon entities that present as cystic lesions in the head and neck are reviewed.

SUMMARY

In this study, peer-reviewed articles were selected using the database PubMed, Google, Google Scholar, and Scopus. Emphasis was placed on peer-reviewed articles that discuss the cytomorphology and differential diagnosis of entities that present as cystic lesions of the head and neck. In the anterior neck, both benign and malignant neoplasms can present, including papillary thyroid carcinoma (PTC), thyroid adenomatoid nodule, parathyroid cysts, and thyroglossal cysts. In the lateral neck, branchial cleft cyst, PTC, ectopic thyroid cyst, and squamous cell carcinomas (human papilloma virus and non- human papilloma virus-related) are common. Age over 40 years raises the possibility of malignancy. In the deep neck, mostly benign cystic entities occur such as a pleomorphic adenoma, paraganglioma, schwannoma, branchial cyst, epidermal inclusion cyst, and lymphoepithelial cyst. Lesions with squamous cell features can pose diagnostic dilemmas.

CONCLUSION

Cytologic examination of head and neck cysts can provide valuable information regarding the nature of the cystic lesions. Information about anatomic site and clinical history can assist with the differential diagnoses. Ancillary studies can improve the diagnosis in some cases. Each case should be evaluated very carefully since there are a wide variety of congenital conditions, infectious/inflammatory conditions, benign neoplasms, and primary and secondary malignancies presenting as a cystic mass in the head and neck.

New Challenges in the Differential Diagnosis of High-Grade Triple-Negative Breast Cancer and Serous Carcinoma

While screening has improved early detection of primary breast cancers, it may also identify metastasis to the breast in rare instances. High-grade carcinomas identified on breast screening may have non-specific morphology and immunoprofiles, making distinction from metastasis problematic. High-grade carcinomas frequently lose expression of specific tumor markers. New evidence specifically challenges GATA3/PAX8 exclusivity in the differential diagnosis of high-grade triple-negative breast cancer and high-grade serous carcinoma of müllerian origin. This case series provides a careful and detailed review of immunohistochemistry interpretation, with focus on PAX8, and the potential pitfalls in making a definitive pathological diagnosis, which is essential in determining oncological treatment options.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Overview of the 2022 WHO Classification of Head and Neck Neuroendocrine Neoplasms

This review article provides a brief overview of the new WHO classification by adopting a question-answer model to highlight the spectrum of head and neck neuroendocrine neoplasms which includes epithelial neuroendocrine neoplasms (neuroendocrine tumors and neuroendocrine carcinomas) arising from upper aerodigestive tract and salivary glands, and special neuroendocrine neoplasms including middle ear neuroendocrine tumors (MeNET), ectopic or invasive pituitary neuroendocrine tumors (PitNET; formerly known as pituitary adenoma) and Merkel cell carcinoma as well as non-epithelial neuroendocrine neoplasms (paragangliomas). The new WHO classification follows the IARC/WHO nomenclature framework and restricts the diagnostic term of neuroendocrine carcinoma to poorly differentiated epithelial neuroendocrine neoplasms. In this classification, well-differentiated epithelial neuroendocrine neoplasms are termed as neuroendocrine tumors (NET), and are graded as G1 NET (no necrosis and < 2 mitoses per 2 mm²; Ki67 < 20%), G2 NET (necrosis or 2-10 mitoses per 2 mm², and Ki67 < 20%) and G3 NET (> 10 mitoses per 2 mm² or Ki67 > 20%, and absence of poorly differentiated cytomorphology). Neuroendocrine carcinomas (> 10 mitoses per 2 mm², Ki67 > 20%, and often associated with a Ki67 > 55%) are further subtyped based on cytomorphological characteristics as small cell and large cell neuroendocrine carcinomas. Unlike neuroendocrine carcinomas, head and neck NETs typically show no aberrant p53 expression or loss of RB reactivity. Ectopic or invasive PitNETs are subtyped using pituitary transcription factors (PIT1, TPIT, SF1, GATA3, ER-alpha), hormones and keratins (e.g., CAM5.2). The new classification emphasizes a strict correlation of morphology and immunohistochemical findings in the accurate diagnosis of neuroendocrine neoplasms. A particular emphasis on the role of biomarkers in the confirmation of the neuroendocrine nature of a neoplasm and in the distinction of various neuroendocrine neoplasms is provided by reviewing ancillary tools that are available to pathologists in the diagnostic workup of head and neck neuroendocrine neoplasms. Furthermore, the role of molecular immunohistochemistry in the diagnostic workup of head and neck paragangliomas is discussed. The unmet needs in the field of head and neck neuroendocrine neoplasms are also discussed in this article. The new WHO classification is an important step forward to ensure accurate diagnosis that will also form the basis of ongoing research in this field.

Overview of the 2022 WHO Classification of Paragangliomas and Pheochromocytomas

This review summarizes the classification of tumors of the adrenal medulla and extra-adrenal paraganglia as outlined in the 5th series of the WHO Classification of Endocrine and Neuroendocrine Tumors. The non-epithelial neuroendocrine neoplasms (NENs) known as paragangliomas produce predominantly catecholamines and secrete them into the bloodstream like hormones, and they represent a group of NENs that have exceptionally high genetic predisposition. This classification discusses the embryologic derivation of the cells that give rise to these lesions and the historical evolution of the terminology used to classify their tumors; paragangliomas can be sympathetic or parasympathetic and the term pheochromocytoma is used specifically for intra-adrenal paragangliomas that represent the classical sympathetic form. In addition to the general neuroendocrine cell biomarkers INSM1, synaptophysin, and chromogranins, these tumors are typically negative for keratins and instead have highly specific biomarkers, including the GATA3 transcription factor and enzymes involved in catecholamine biosynthesis: tyrosine hydroxylase that converts L-tyrosine to L-DOPA as the rate-limiting step in catecholamine biosynthesis, dopamine beta-hydroxylase that is present in cells expressing norepinephrine, and phenylethanolamine N-methyltransferase, which converts norepinephrine to epinephrine and therefore can be used to distinguish tumors that make epinephrine. In addition to these important tools that can be used to confirm the diagnosis of a paraganglioma, new tools are recommended to determine genetic predisposition syndromes; in addition to the identification of precursor lesions, molecular immunohistochemistry can serve to identify associations with SDHx, VHL, FH, MAX, and MEN1 mutations, as well as pseudohypoxia-related pathogenesis. Paragangliomas have a well-formed network of sustentacular cells that express SOX10 and S100, but this is not a distinctive feature, as other epithelial NENs also have sustentacular cells. Indeed, it is the presence of such cells and the association with ganglion cells that led to a misinterpretation of several unusual lesions as paragangliomas; in the 2022 WHO classification, the tumor formerly known as cauda equina paraganglioma is now classified as cauda equina neuroendocrine tumor and the lesion known as gangliocytic paraganglioma has been renamed composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). Since the 4th edition of the WHO, paragangliomas have no longer been classified as benign and malignant, as any lesion can have metastatic potential and there are no clear-cut features that can predict metastatic behavior. Moreover, some tumors are lethal without metastatic spread, by nature of local invasion involving critical structures. Nevertheless, there are features that can be used to identify more aggressive lesions; the WHO does not endorse the various scoring systems that are reviewed but also does not discourage their use. The identification of metastases is also complex, particularly in patients with germline predisposition syndromes, since multiple lesions may represent multifocal primary tumors rather than metastatic spread; the identification of paragangliomas in unusual locations such as lung or liver is not diagnostic of metastasis, since these may be primary sites. The value of sustentacular cells and Ki67 labeling as prognostic features is also discussed in this new classification. A staging system for pheochromocytoma and extra-adrenal sympathetic PGLs, introduced in the 8th Edition AJCC Cancer Staging Manual, is now included. This paper also provides a summary of the criteria for the diagnosis of a composite paragangliomas and summarizes the classification of neuroblastic tumors. This review adopts a practical question-answer framework to provide members of the multidisciplinary endocrine oncology team with a most up-to-date approach to tumors of the adrenal medulla and extra-adrenal paraganglia.

Overview of the 2022 WHO Classification of Parathyroid Tumors

The 2022 WHO classification reflects increases in the knowledge of the underlying pathogenesis of parathyroid disease. In addition to the classic characteristic features of parathyroid neoplasms, subtleties in histologic features which may indicate an underlying genetic abnormality reflect increased understanding of the clinical manifestations, histologic, and genetic correlation in parathyroid disease. The importance of underlying genetic aberrancies is emphasized due to their significance to the care of the patient. Traditionally, the term "parathyroid hyperplasia" has been applied to multiglandular parathyroid disease; however, the concept of hyperplasia is generally no longer supported in the context of primary hyperparathyroidism since affected glands are usually composed of multiple "clonal" neoplastic proliferations. In light of these findings and management implications for patient care, the 2022 WHO classification endorses primary hyperparathyroidism-related multiglandular parathyroid disease (multiglandular multiple parathyroid adenomas) as a germline susceptibility-driven multiglandular parathyroid neoplasia. From such a perspective, pathologists can provide additional value to genetic triaging by recognizing morphological and immunohistochemical harbingers of MEN1, CDKN1B, MAX, and CDC73-related manifestations. In the current WHO classification, the term "parathyroid hyperplasia" is now used primarily in the setting of secondary hyperplasia which is most often caused by chronic renal failure. In addition to expansion in the histological features, including those that may be suggestive of an underlying genetic abnormality, there are additional nomenclature changes in the 2022 WHO classification reflecting increased understanding of the underlying pathogenesis of parathyroid disease. The new classification no longer endorses the use of "atypical parathyroid adenoma". This entity is now being replaced with the term of "atypical parathyroid tumor" to reflect a parathyroid neoplasm of uncertain malignant potential. The differential diagnoses of atypical parathyroid tumor are discussed along with the details of worrisome clinical and laboratory findings, and also features that define atypical histological and immunohistochemical findings to qualify for this diagnosis. The histological definition of parathyroid carcinoma still requires one of the following findings: (i) angioinvasion (vascular invasion) characterized by tumor invading through a vessel wall and associated thrombus, or intravascular tumor cells admixed with thrombus, (ii) lymphatic invasion, (iii) perineural (intraneural) invasion, (iv) local malignant invasion into adjacent anatomic structures, or (v) histologically/cytologically documented metastatic disease. In parathyroid carcinomas, the documentation of mitotic activity (e.g., mitoses per 10mm²) and Ki67 labeling index is recommended. Furthermore, the importance of complete submission of parathyroidectomy specimens for microscopic examination, and the crucial role of multiple levels along with ancillary biomarkers have expanded the diagnostic workup of atypical parathyroid tumors and parathyroid carcinoma to ensure accurate characterization of parathyroid neoplasms. The concept of parafibromin deficiency has been expanded upon and term "parafibromin deficient parathyroid neoplasm" is applied to a parathyroid neoplasm showing complete absence of nuclear parafibromin immunoreactivity. Nucleolar loss is considered as abnormal finding that requires further molecular testing to confirm its biological significance. The 2022 WHO classification emphasizes the role of molecular immunohistochemistry in parathyroid disease. By adopting a question-answer framework, this review highlights advances in knowledge of histological features, ancillary studies, and associated genetic findings that increase the understanding of the underlying pathogenesis of parathyroid disease that are now reflected in the updated classification and new entities in the 2022 WHO classification.

Overview of the 2022 WHO Classification of Neuroendocrine Neoplasms

In this review, we detail the changes and the relevant features that are applied to neuroendocrine neoplasms (NENs) in the 2022 WHO Classification of Endocrine and Neuroendocrine Tumors. Using a question-and-answer approach, we discuss the consolidation of the nomenclature that distinguishes neuronal paragangliomas from epithelial neoplasms, which are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The criteria for these distinctions based on differentiation are outlined. NETs are generally (but not always) graded as G1, G2, and G3 based on proliferation, whereas NECs are by definition high grade; the importance of Ki67 as a tool for classification and grading is emphasized. The clinical relevance of proper classification is explained, and the importance of hormonal function is examined, including eutopic and ectopic hormone production. The tools available to pathologists for accurate classification include the conventional biomarkers of neuroendocrine lineage and differentiation, INSM1, synaptophysin, chromogranins, and somatostatin receptors (SSTRs), but also include transcription factors that can identify the site of origin of a metastatic lesion of unknown primary site, as well as hormones, enzymes, and keratins that play a role in functional and structural correlation. The recognition of highly proliferative, well-differentiated NETs has resulted in the need for biomarkers that can distinguish these G3 NETs from NECs, including stains to determine expression of SSTRs and those that can indicate the unique molecular pathogenetic alterations that underlie the distinction, for example, global loss of RB and aberrant p53 in pancreatic NECs compared with loss of ATRX, DAXX, and menin in pancreatic NETs. Other differential diagnoses are discussed with recommendations for biomarkers that can assist in correct classification, including the distinctions between epithelial and non-epithelial NENs that have allowed reclassification of epithelial NETs in the spine, in the duodenum, and in the middle ear; the first two may be composite tumors with neuronal and glial elements, and as this feature is integral to the duodenal lesion, it is now classified as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). The many other aspects of differential diagnosis are detailed with recommendations for biomarkers that can distinguish NENs from non-neuroendocrine lesions that can mimic their morphology. The concepts of mixed neuroendocrine and non-neuroendocrine (MiNEN) and amphicrine tumors are clarified with information about how to approach such lesions in routine practice. Theranostic biomarkers that assist patient management are reviewed. Given the significant proportion of NENs that are associated with germline mutations that predispose to this disease, we explain the role of the pathologist in identifying precursor lesions and applying molecular immunohistochemistry to guide genetic testing.

Parathyroid Carcinoma: a Review

Parathyroid cancer is a rare endocrine malignancy with only a few thousand cases reported worldwide. As a result, there exists considerable controversy regarding the various aspects of this disease, viz., etiology, diagnosis, and management. We hereby attempt to review the literature on parathyroid carcinoma (PC) and summarize the practices based on the current evidence available. The majority of the PC are sporadic although an association with hyperparathyroidism-jaw tumor syndrome, multiple endocrine neoplasia (MEN) 1 and 2, and isolated familial hyperparathyroidism has been shown. As preoperative diagnosis is challenging, PC should be suspected in patients presenting with a neck mass with signs and symptoms of invasion to surrounding structures. Skeletal and renal symptoms are often associated with PC as presenting complaints. The biochemical parameters are more pronounced in the case of PC compared with benign countpart. Due to its rarity, the American Joint Committee of cancer control (AJCC) acknowledges that as yet a clear distinct staging system to prognosticate the disease would be premature. Complete excision with negative margins at first surgery offers the best chance of cure. The role of radiotherapy (RT) is still unclear; however few series have suggested a better locoregional control with adjuvant RT. Recurrences are common and are most significantly associated with an incomplete clearance at initial surgery. Surgical salvage of recurrent/metastatic disease with medical management of hypercalcemia is the treatment of choice. Large prospective studies and trials need to be conducted to understand the pathology better and improve management protocols; however this is a challenge due to rarity of cases.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

Hsa_circ_0005729 enhances accuracy in diagnosing parathyroid carcinoma

BACKGROUND

Parathyroid carcinoma (PC), often misdiagnosed as a parathyroid adenoma (PA), is prone to local relapse due to the initial surgery being restricted to parathyroid lesions instead of en bloc resection of parathyroid lesions with negative incision margins. However, it is very challenging to distinguish PC from PA preoperatively; hence, this study investigated an effective biomarker for increasing accuracy in PC diagnosis.

METHOD

First, the differentially expressed circular RNAs between three PC tissues and three PA tissues were screened by high-throughput circular RNA sequencing, and the expression of hsa_circ_0005729 was verified by qRT-PCR in 14 patients with PC and 40 patients with PA. Secondly, the receiver operating characteristic curve and the area under the curve (AUC) were used to analyze the diagnostic efficiency of hsa_circ_0005729 in PC by combining with laboratory data. Thirdly, RNF138mRNA, the corresponding linear transcript of hsa_circ_0005729, was measured, and the relationship between hsa_circ_0005729 and RNF138 mRNA was analyzed in patients with PA and patients with PC.

RESULTS

Hsa_circ_0005729 expression was significantly higher in patients with PC than in patients with PA. Serum calcium (P = 0.045), alkaline phosphatase (ALP) (P = 0.048), and creatinine levels (P = 0.036) were significantly higher in patients with PC than in patients with PA. The AUC increased to 0.86 when hsa_circ_0005729 combined with serum calcium, creatinine, and ALP. In addition, hsa_circ_0005729 was positively correlated with RNF138 mRNA in patients with PA but not in patients with PC.

CONCLUSION

The novel circular RNA hsa_circ_0005729 was found to have a higher expression in patients with PC, indicating its usefulness for distinguishing PC from PA.

Histopathological Features of Parathyroid Adenoma and 18F-Choline Uptake in PET/MR of Primary Hyperparathyroidism

BACKGROUND

The aim of this study was to assess the relationship between the histopathological properties of hyperfunctioning parathyroids and parathyroid 18F-choline uptake.

PATIENTS AND METHODS

A total of 31 parathyroid adenomas were retrospectively analyzed in patients with primary hyperparathyroidism and preoperative 18F-choline PET/MR. PET/MR parameters of parathyroid glands (SUVmax and target-to-background ratio in early-phase [EP] and late-phase [LP]), MRI volume, preoperative parathyroid hormone (PTH) serum concentration, and postoperative histopathology (predominant cell type and growth pattern of adenoma cells, location and size of adenoma) were assessed. The relationship of PET/MR parameters, PTH, and histological parameters was determined using linear regression, Spearman correlation and Kruskal-Wallis test.

RESULTS

The median volume of parathyroid adenoma was 421.78 ± 142.46 mm3 (46.39-4412.69). Adenomas were predominantly composed of chief, water-clear, and oncocytic/oxyphilic cells in 27/31, 2/31, and 2/31 cases, respectively. The growth pattern was predominantly solid, follicular, and trabecular in 18/31, 8/31, and 5/31, respectively. The SUVmax was 6.71 ± 3.39 in EP and 6.91 ± 3.97 in LP. Follicular growth pattern had slightly higher EP SUVmax (trabecular: 4.12 ± 0.56; solid: 6.62 ± 3.19; follicular: 8.56 ± 3.96; P = 0.046). Spearman correlation showed strong positive correlation between volume and both EP and LP SUVmax (0.626; P = 0.0001 and 0.576; P = 0.0001, respectively). Linear regression analysis revealed significant correlation between PTH level and EP and LP SUVmax (both P = 0.001); in contrast, no correlation was found between PTH level and both cell type and growth pattern.

CONCLUSIONS

Our findings suggest that 18F-choline uptake of parathyroid adenomas might be associated both with the histological growth pattern and adenoma volume, but not with a specific cell type.

Parathyroid Carcinoma and Adenoma Co-existing in One Patient: Case Report and Comparative Proteomic Analysis

BACKGROUND/AIM

The lack of specific parathyroid carcinoma (PC) biomarkers in clinical practice points out the importance of analyzing the proteomic signature of this cancer. We performed a comparative proteomic analysis of PC and parathyroid adenoma (PA) co-existing in the same patient.

PATIENTS AND METHODS

PC and PA were taken from a 63-year-old patient. Using two-dimensional differential gel electrophoresis (2D-DIGE) coupled to mass spectrometry we examined the differences between PC and PA proteins. For validation, additional PC and PA samples were obtained from 10 patients. Western blot analysis was used to validate the difference of expression observed with 2D-DIGE analysis. Bioinfomatic analysis was performed using QIAGEN's Ingenuity Pathways Analysis (IPA) to determine the predominant canonical pathways and interaction networks involved.

RESULTS

Thirty-three differentially expressed proteins were identified in PC compared to PA. Among these, ubiquitin C-terminal hydrolase-L1 (UCH-L1) was highly overexpressed in PC. The result was confirmed by Western Blot analysis in additional PC samples.

CONCLUSION

Our comparative proteomic analysis of co-existing neoplasms allowed detecting specific and peculiar differences between PC and PA overcoming population biological variability.

Ex Vivo Intact Tissue Analysis Reveals Alternative Calcium-sensing Behaviors in Parathyroid Adenomas

CONTEXT

The biochemical basis for clinical variability in primary hyperparathyroidism (PHPT) is poorly understood.

OBJECTIVE

This study aimed to define parathyroid tumor biochemical properties associated with calcium-sensing failure in PHPT patients, and to relate differences in these profiles to variations in clinical presentation.

METHODS

Preoperative clinical data from a sequential series of 39 patients undergoing surgery for PHPT at an endocrine surgery referral center in a large, public university hospital were evaluated for correlation to parathyroid tumor biochemical behavior. An intact tissue, ex vivo interrogative assay was employed to evaluate the calcium-sensing capacity of parathyroid adenomas relative to normal donor glands. Tumors were functionally classified based on calcium dose-response curve profiles, and clinical parameters were compared among the respective classes. Changes in the relative expression of 3 key components in the calcium/parathyroid hormone (PTH) signaling axis-CASR, RGS5, and RCAN1-were evaluated as potential mechanisms for calcium-sensing failure.

RESULTS

Parathyroid adenomas grouped into 3 distinct functional classes. Tumors with diminished calcium sensitivity were the most common (18 of 39) and were strongly associated with reduced bone mineral density (P = 0.0009). Tumors with no calcium-sensing deficit (11 of 39) were associated with higher preoperative PTH (P = 0.036). A third group (6/39) displayed a nonsigmoid calcium/PTH response curve; 4 of these 6 tumors expressed elevated RCAN1.

CONCLUSION

Calcium-sensing capacity varies among parathyroid tumors but downregulation of the calcium-sensing receptor (CASR) is not an obligate underlying mechanism. Differences in tumor calcium responsiveness may contribute to variations in PHPT clinical presentation.

Management and Outcome of Parathyroid Carcinoma-Induced Primary Hyperparathyroidism: A Single-Centre Experience

BACKGROUND

Parathyroid carcinoma (PC) is the rarest endocrine cancer and an infrequent cause of primary hyperparathyroidism (PHPT), responsible for less than 1% of cases. Due to its rarity, treatment is challenging.

METHODS

A retrospective cohort study on 462 patients referred for parathyroidectomy to Thyroid and Parathyroid Unit at Santi Paolo e Carlo Hospital, Milan, Italy, from 2011 to 2021. We identified and individually described the patients affected with PC. Then, we split all patients treated for PHPT into four groups based on the cause: PC, adenoma, atypical adenoma, and hyperplasia. Patients' demographics, preoperative evaluation results, intraoperative findings, and outcomes for the PC group were compared with groups of PHPT due to benign causes.

RESULTS

Eight cases of PC were identified, five males and three females. Seven cases presented with symptoms of hypercalcemia and one with a neck mass. Five underwent en bloc resections and three local excisions. Histopathological features showed capsular invasion in four patients, capsular and soft tissue invasion in three patients, and vascular invasion in one case. No patients had distant metastasis. One patient was classed as high risk based on the Schulte classification system. All patients treated for PC were alive and disease-free at a mean follow-up of 38.4 months. When compared with other PHPT patients, PC patients were more frequently male and had higher preoperative blood calcium and PTH and lower phosphate levels, larger and heavier parathyroids excised, lower postoperative calcium, and a higher rate of postoperative hypoparathyroidism.

CONCLUSION

Our study highlights some aspects valuable to suspect PC and differentiate PHPT-PC from benign causes of PHPT preoperatively. Preoperative suspicion of malignancy is essential to guarantee the best course of treatment for patients. Although limited for size and follow-up, the excellent outcome of our series seems to support the value of both surgery extension and risk class according to the Schulte classification as possible prognostic factors for recurrence.

Are Non-Coding RNAs Useful Biomarkers in Parathyroid Tumorigenesis?

Tumors of the parathyroid glands are common endocrine diseases almost always characterized by parathyroid hormone hypersecretion that determines the clinical manifestations of primary hyperparathyroidism, such as fatigue, kidney problems, weakness, brittle bones, and other symptoms. Most parathyroid neoplasia are benign adenomas, although rare malignant forms have been described. They are heterogeneous in terms of clinical presentation and the associated signs and symptoms overlap with those of disease and aging. Furthermore, most patients with hypercalcemia are discovered during routine blood tests for other reasons. Surgical removal is considered the main therapeutic option to cure these endocrine tumors and, therefore, innovative therapeutic approaches are actively required. Recently, a growing number of studies have suggested that alterations to the epigenetic mechanisms could play a pivotal role in parathyroid tumorigenesis. Most of the attention has been focused on non-coding RNAs (ncRNAs) (i.e., miRNAs, lncRNAs, and circRNAs) whose expression profile has been found to be deregulated in parathyroid tumors. The aim of the present paper is to give an insight into the ncRNAs involved in parathyroid tumorigenesis, which could be used in the future either as innovative diagnostic biomarkers or as therapeutic targets for the treatment of this endocrine neoplasia.

Second-Generation Neuroendocrine Immunohistochemical Markers: Reflections from Clinical Implementation

Simple Summary

Neuroendocrine tumors are a collection of neoplastic lesions arising in cells with traits similar to hormone-producing and nerve cells with the ability to secrete peptide hormones using an intricate vesicle transportation system. From a clinical standpoint, neuroendocrine tumors are unique in terms of therapeutic modalities, and a correct diagnosis is therefore imperative in order for the patient to obtain the most efficient treatment. In this process, the pathologist can analyze if the tumor cells express Chromogranin A and Synaptophysin, two proteins associated with the regulation of secretory vesicles. Unfortunately, these markers are not always present in neuroendocrine tumors, and non-neuroendocrine tumors may also occasionally express Chromogranin A or Synaptophysin—making the diagnosis difficult to make for certain cases. Recently, three proteins termed ISL1, INSM1 and Secretagogin were found to be selectively expressed in neuroendocrine cells, and subsequent studies have identified their potential as markers of neuroendocrine differentiation in the clinical setting. In this commentary, the benefits of these novel “second-generation” markers are briefly discussed from a clinical context.

Abstract

When analyzing tumors by histopathology, endocrine pathologists have traditionally been restricted to a few key immunohistochemical markers related to secretory vesicles in order to pinpoint neuroendocrine differentiation—most notably Chromogranin A (CGA) and Synaptophysin (SYP). Although proven of great clinical utility, these markers sometimes exhibit tissue-specific patterns depending on tumor origin, and non-neuroendocrine tumors might sometimes display focal expression. Moreover, CGA and SYP might be partially or totally absent in highly proliferative neuroendocrine carcinomas, making the diagnosis particularly challenging on small biopsies of metastatic lesions with unknown location of the primary tumor. The advent of second-generation neuroendocrine markers ISL LIM Homeobox 1 (ISL1), INSM Transcriptional Repressor 1 (INSM1) and Secretagogin (SECG) have expanded the pathology toolbox considerably, constituting markers that often retain expression even in poorly differentiated neuroendocrine carcinomas. As non-neuroendocrine tumors seldom express these antigens, the specificity of ISL1, INSM1 and SECG make them welcome additions to clinical practice. In this commentary, recent advances of this field as well as initial clinical experiences from a tertiary neuroendocrine center are discussed.

Monoclonal/polyclonal PAX-8, PTH and GATA3 immunohistochemistry in parathyroid lesions

BACKGROUND

Parathyroid gland (PG) is an endocrine organ which may display different immunohistochemical stainings with chief cells and oxyphilic cells in normal as well as hyperplasic/tumoral lesions.

PURPOSE

In this study, we aimed to identify the demographic properties and diagnostic value of the GATA3 antibody, which is a transcription factor in addition to PTH, and of PAX-8 (monoclonal and polyclonal) antibody.

METHODS

We have analyzed in detail the cellular components and staining intensities of 46 adenomas all of which contained parathyroid rims, 12 hyperplasia and 5 adjacent non-neoplastic thyroidectomy materials (63 patients, 114 tissues).

RESULTS

While no staining was identified in the thyroid tissue, cytoplasmic PTH immunoreactivity was observed in all (100%) normal parathyroid tissues, rim of PGs and hyperplasia, and in 43/46 cases (93.4%) of adenomas. Adenoma and hyperplasia were less stained than normal PG (p < 0.05). We detected GATA3 staining in all cases except for the thyroid (100%). Weak positivity (1+) was most apparent in adenoma cases (p < 0.05). Monoclonal PAX-8 immunoreactivity was not identified in any normal parathyroid tissue and rim of PG but positive immunoreactivity was detected in 83.3% of hyperplasia cases (10/12), 84.8% of adenoma (39/46) and 100% of thyroid tissues (5/5) (p < 0.05). However, polyclonal PAX-8 immunoreactivity was detected in one normal parathyroid tissue (1/5) and seven (7/46) rim of PGs. In cases of hyperplasia and adenoma, positive immunoreactivity was 75% (9/12) and 74% (34/46), respectively.

CONCLUSION

In conclusion, we have observed that PTH and GATA3 constitute a much more reliable and sensitive marker for parathyroid and are stained less in adenomas. While monoclonal PAX-8 (MRQ-50) never stains normal parathyroid and rim of PGs, it may help in the differential diagnosis of proliferated parathyroid lesions as a considerably sensitive and relatively specific marker by staining hyperplasic parathyroid, adenomas and the thyroid.

Distinguishing Parathyromatosis, Atypical Parathyroid Adenomas, and Parathyroid Carcinomas Utilizing Histologic and Clinical Features

Parathyromatosis is displaced parathyroid tissue in the neck and mediastinum related to prior surgery. Parathyromatosis can be difficult to distinguish from atypical adenoma and parathyroid carcinoma. The aim of this study is to evaluate clinical and morphologic features that may differentiate parathyromatosis, atypical adenoma, and parathyroid carcinoma. Cases of parathyromatosis, atypical adenoma, and parathyroid carcinoma were identified. Index cases were reviewed by consensus for histologic features, including stromal, cytologic/architectural, and invasive features. Ki67 was performed on index cases and scored using the Adsay method. Clinical information was gathered from the electronic medical record. 4 parathyromatosis, 17 atypical adenoma, and 6 parathyroid carcinoma were included. Parathyroid carcinomas were more likely to display coarse chromatin with nucleoli (P = 0.04), infiltrative invasion (P < 0.01), and metastasis (P < 0.01). Only parathyromatosis showed circumscribed invasion. Infiltrative invasion was more common in cases with progression (P = 0.046) and metastasis (P < 0.001). Necrosis and perineural invasion were only present in cases with progression and were more frequent in cases with metastasis (P = 0.079 and P = 0.19, respectively). There were no differences in presence of a fibrous capsule, capsular invasion, intralesional fibrous bands, random endocrine atypia, solid growth, Ki67 index, gland size/weight, serum PTH/calcium levels, and locoregional recurrence rates. There is overlap in the histologic features in parathyromatosis, atypical adenoma, and parathyroid carcinoma. While perineural, vascular, and infiltrative soft tissue invasion should remain diagnostic of malignancy, other atypical features such as solid growth, coarse chromatin with nucleoli, and necrosis should raise concern for recurrence and/or metastasis, and can be present in parathyroid lesions with and without recurrence.

Genomics and Epigenomics in Parathyroid Neoplasia: from Bench to Surgical Pathology Practice

The majority of parathyroid disease encountered in routine practice is due to single parathyroid adenoma, of which the majority arise as sporadic tumors. This is usually a straightforward diagnosis in endocrine pathology when in the appropriate clinical setting, although subsets of cases will exhibit atypical histological features that may warrant additional immunohistochemical and genetic analyses to estimate the malignant potential. Parathyroid carcinomas on the other hand, are bona fide malignant tumors characterized by their unequivocal invasion demonstrated through routine histology or metastasis. The ultimate endpoint for any molecular marker discovered through laboratory investigations is to be introduced in clinical routine practice and guide the surgical pathologist in terms of diagnostics and prognostication. For parathyroid tumors, the two main diagnostic challenges include the distinction between parathyroid adenoma and parathyroid carcinoma, as well as the pinpointing of hereditable disease for familial screening purposes. While numerous markers on genetic, epigenetic, and protein levels have been proposed as discriminative in these aspects, this review aims to condense the scientific coverage of these enigmatic topics and to propose a focused surgical pathology approach to the subject.

Case Report and Systematic Review: Sarcomatoid Parathyroid Carcinoma-A Rare, Highly Malignant Subtype

BACKGROUND

Parathyroid carcinoma (PC) is a rare malignancy, the incidence of which is less than 1/1 million per year. Sarcomatoid parathyroid carcinoma (SaPC) is an extremely peculiar subtype; only three cases have been reported internationally. It consists of both malignant epithelial components and sarcomatoid components (mesenchymal origin) simultaneously. This "confusing" cancer exhibits higher invasiveness, and traditional surgery does not appear to achieve the expectation, which differs significantly from that of general PC.

OBJECTIVE

To characterize the clinicopathologic features of SaPC and explore similarities and differences between SaPC and general PC.

MATERIALS AND METHODS

We collected clinical data of SaPC cases from our center and literature. The SaPC case in our center was presented. To better understand the characteristics of SaPC, we also reviewed clinical information in general PC cases from our center and literature within the last 5 years, and a systematic review was performed for further comparison.

RESULTS

A 60-year-old woman was admitted for a neck mass and hoarseness. After the surgery, she was confirmed as SaPC and ultimately developed local recurrence at 3 months. Together with the reported cases from literature, four cases of SaPC (three cases from literature) and 203 cases of general PC (200 cases from literature) were reviewed. Both tumors showed obvious abnormalities in parathormone (PTH) level and gland size. Compared to general PC, SaPC has a later age of onset (60.50 ± 7.42 vs. 51.50 ± 8.29), relatively low levels of PTH (110.28 ± 59.32 vs. 1,156.07 ± 858.18), and a larger tumor size (6.00 ± 1.63 vs. 3.14 ± 0.70). For SaPC, all four cases were initially misdiagnosed as thyroid tumors (4/4). Spindle cell areas or transitional zones were common pathological features in SaPC cases (3/4).

CONCLUSION

SaPC is a very rare pathologic subtype of PC and appears to be much more easily misdiagnosed as a thyroid tumor. Spindle cell areas or transitional zones are highly possible to be pathological features in its sarcomatoid components. Despite many similarities, there are some differences between SaPC and general PC-SaPC does not show the obvious endocrine feature but stronger aggressiveness. Surgical treatment of SaPC does relieve life-threatening symptoms and improve quality of life even with recurrence in the short term.

Parathyroid carcinoma with sarcomatoid differentiation: a case report and literature review

Background

Parathyroid carcinoma (PC) is a rare thyroid tumor. PC with sarcomatoid differentiation(PCSD) is even rarer and its exact etiology remains unclear. We here report a case of PCSD, and present the clinicopathological features and pathological diagnosis and review the literature.

Case presentation

A 71-year-old man presented with a mass of 4.5 cm × 3.5 cm in the right neck. The tumor was composed of nest-like transparent cells, and the septum had heterotypic rhabdoid cells with sarcomatoid differentiation. Immunophenotype was as follows: myogenic differentiation 1(MyoD1), myogenin and desmin were positive; clear cells were positive for chromogranin A(CGA), synaptophysin(Syn) and GATA-3; and Ki-67 proliferation index was 40%. Hematoxylin and eosin staining and immunohistochemistry were performed. The patient was diagnosed with PCSD, and died 6 months after surgery.

Conclusions

PCSD is a rare type of primary parathyroid tumor with high malignancy and poor prognosis. Definitive diagnosis should be based on histopathological morphology and immunophenotype, and surgical treatment should be performed as soon as possible.

[Neuroendocrine markers in parathyroid tumors]

The parathyroid glands (PTGs) are a key regulator of calcium and phosphorus metabolism in the human body. In terms of their, morphological and immunophenotypic characteristics, PTGs are neuroendocrine organs, and their neoplasms are neuroendocrine tumors. These neoplasms include adenoma and cancer; in addition, glandular hyperplasia may develop, which is most characteristic of multiple endocrine neoplasia (MEN1, MEN2a, and MEN4) syndromes. The morphological characteristics of pathologically altered PTGs in MEN syndromes are variable. The analysis and generalization of knowledge about the features and expression of various immunohistochemical markers in PTG tissue in health and in diseases are useful in the practical work of not only pathologists, but also clinicians of various specialties.

Parathyroid Carcinoma in the Setting of Tertiary Hyperparathyroidism: Case Report and Review of the Literature

INTRODUCTION

Parathyroid carcinoma is one of the rarest cancers in normal population, and it is extremely uncommon in the setting of tertiary hyperparathyroidism. Indeed, only 24 cases have been reported in the literature. Presentation of the Case. We report the case of parathyroid carcinoma in a 51-year-old man, with a history of end-stage renal disease due to a horseshoe kidney treated with haemodialysis since 2013. He came to our attention due to an increase in calcium and parathyroid hormone serum levels. Neck ultrasound (US) showed a solid hypodense mass, probably the right inferior parathyroid gland, with an estimated size of 25 × 15 × 13 mm; the 99mTc-sestamibi SPECT/CT scan revealed a large radiotracer activity area in the right cervical region, compatible with a hyperfunctioning right inferior parathyroid gland. So, a tertiary hyperparathyroidism diagnosis was made. In April 2018, resection of three parathyroid glands was performed. Histopathological examination demonstrated the right inferior parathyroid gland specimen to be a parathyroid carcinoma, due to the presence of multiple, full-thickness, capsular infiltration foci, and a venous vascular invasion focus. Discussion. Diagnosis of parathyroid carcinoma in tertiary hyperparathyroidism is remarkably complex because of the lack of clinical diagnostic criteria and, in many cases, is made postoperatively at histopathological examination.

CONCLUSION

To date, radical surgery represents the mainstay of treatment, with a five- and ten-year survival rates overall acceptable.

Major Clues and Pitfalls in the Differential Diagnosis of Parathyroid and Thyroid Lesions Using Fine Needle Aspiration Cytology

Background: It is difficult to distinguish parathyroid lesions (PLs) from thyroid lesions using fine needle aspiration cytology (FNAC) because of their proximity and their similar cytomorphological features. Methods: FNAC smears of 46 patients with pathologically proven PLs that were histologically diagnosed as parathyroid adenoma (PA, n = 35), parathyroid hyperplasia (PH, n = 3), atypical parathyroid adenoma (APA, n = 1), and parathyroid carcinoma (PC, n = 7) were retrospectively reviewed and analyzed. Results: Our initial cytological diagnoses indicated correct diagnoses in 31 of 46 PL patients (67%). The 15 erroneous diagnoses were 5 patients with non-specific benign disease (11%), 4 with nodular hyperplasia of the thyroid (9%), 5 with atypical cells (11%), and 1 with a metastatic papillary thyroid carcinoma (2%). Follicular pattern, papillary structures, colloid-like material, and macrophages, which often suggest thyroid lesions, were also present in some PLs. We found that branching capillaries along the papillary structures, stippled nuclear chromatin, and frequent occurrence of naked nuclei were useful for determining a parathyroid origin. Conclusions: It is important to be aware that PLs are frequently mistaken for thyroid lesions based on FNAC. The specific and unique characteristics of PLs identified here may be helpful in diagnosis.

Immunocyte density in parathyroid carcinoma is correlated with disease relapse

PURPOSE

Parathyroid carcinoma (PC) is an endocrine malignancy with a poor prognosis. The tumour immune microenvironment is a critical factor influencing the outcomes of multiple cancer types. However, knowledge of the immune microenvironment in PC remains limited.

METHODS

The intratumoural density of immunocytes and the Ki-67 index were evaluated immunohistochemically in 51 PC patient samples and were compared with clinicopathological features and parafibromin staining results. The Kaplan-Meier method and Cox proportional hazards analysis were used to estimate the effects of these variables on clinical outcomes.

RESULTS

Intratumoural immunocyte density was not correlated with age, gender, urolithiasis, or palpation of a neck mass. The Ki-67 index was correlated with the intratumoural density of CD3⁺ cells (P = 0.022) and CD8⁺ cells (P = 0.021) and serum calcium levels (P = 0.022). In the intratumoural area of primary foci, Kaplan-Meier method showed that the risk factors associated with recurrence/metastasis were a low density of CD3⁺ (P = 0.017), CD8⁺ (P = 0.019) and CD45⁺ cells (P = 0.047), a high density of CD163⁺ cells (P = 0.003) and a high Ki-67 index (P = 0.004). Cox regression multivariate analysis revealed that CD163⁺ cell density (hazard ratio (HR) 16.19, 95% confidence interval (CI) 1.99-131.66; P = 0.009) and CD8⁺ cell density (HR 0.13, 95% CI 0.02-0.76, P = 0.024) were independent factors associated with PC relapse.

CONCLUSION

The immune microenvironment is an important factor influencing the relapse of PC. The intratumoural density of CD3⁺, CD8⁺, CD45⁺, and CD163⁺ immunocytes was correlated with disease-free survival (DFS) in patients with PC. Immunotherapy based on T lymphocytes or tumour-associated macrophages may be a promising treatment strategy.

Pitfalls in Challenging Thyroid Tumors: Emphasis on Differential Diagnosis and Ancillary Biomarkers

Thyroid pathology encompasses a heterogenous group of clinicopathological entities including rare and diagnostically challenging neoplasms. The review is focused on morphological, immunohistochemical, and molecular features of rare thyroid neoplasms that can pose diagnostic problems. The tumors are organized based on growth patterns including thyroid neoplasms with predominantly papillary, follicular, solid, and spindle cell growth pattern, as well as neoplasms with distinct cytological characteristics. A special section is also dedicated to rare thyroid tumors with peculiar patterns including thyroid carcinoma with Ewing family tumor elements and intrathyroidal thymic-related neoplasms.

[99mTc]Sestamibi SPECT Can Predict Proliferation Index, Angiogenesis, and Vascular Invasion in Parathyroid Patients: A Retrospective Study

The aim of this study was to evaluate the possible association among sestamibi uptake and the main histopathological characteristics of parathyroid lesions related to aggressiveness such as the proliferation index (Ki67 expression and mitosis), angiogenesis (number of vessels), and vascular invasion in hyperparathyroidism patients. To this end, 26 patients affected by primary hyperparathyroidism subjected to both scintigraphy with [99mTc]Sestamibi and surgery/bioptic procedure were retrospectively enrolled. Hyperfunctioning of the parathyroid was detected in 19 patients. Our data showed a significant positive association among the sestamibi uptake and the proliferation index histologically evaluated both in terms of the number of Ki67 positive cells and mitosis. According to these data, lesions with a higher valuer of L/N (lesion to nonlesion ratio) frequently showed several vessels in tumor areas and histological evidence of vascular invasion. It is noteworthy that among patients with negative scintigraphy, 2 patients showed a neoplastic lesion after surgery (histological analysis). However, it is important to highlight that these lesions displayed very low proliferation indexes, which was evaluated in terms of number of both mitosis and Ki67-positive cells, some/rare vessels in the main lesion, and no evidence of vascular invasion. In conclusion, data obtained on patients with positive or negative scintigraphy support the hypothesis that sestamibi can be a tracer that is capable of predicting some biological characteristics of parathyroid tumors such as angiogenesis, proliferation indexes, and the invasion of surrounding tissues or vessels.

Intratumor heterogeneity in human parathyroid tumors

Parathyroid tumors are the second most common endocrine neoplasia after thyroid neoplasia. They are mostly associated with impaired parathormone (PTH) synthesis and release determining the metabolic and clinical condition of primary hyperparathyroidism (PHPT). PHPT is the third most prevalent endocrine disorder, mainly affecting postmenopausal women. Parathyroid benign tumors, both adenomas of a single gland or hyperplasia involving all the glands, are the main histotypes, occurring in more than 95% of PHPT cases. The differential diagnosis between benign and malignant parathyroid lesions is a challenge for clinicians. It relies on histologic features, which display significant overlap between the histotypes with different clinical outcomes. Parathyroid adenomas and hyperplasia have been considered so far as a unique monoclonal/polyclonal entity, while accumulating evidence suggest great heterogeneity. Intratumor parathyroid heterogeneity involves tumor cell type, as well as tumor cell function, in terms of PTH synthesis and secretion, and of expression patterns of membrane and nuclear receptors (calcium sensing receptor, vitamin D receptor, α-klotho receptor and others). Intratumor heterogeneity can also interfere with cell molecular biology, in regard to clonality, oncosuppressor gene expression (such as MEN1 and HRPT2/CDC73), transcription factors (GCM2, TBX1) and microRNA expression. Such heterogeneity is likely involved in the phenotypic variability of the parathyroid tumors, and it should be considered in the clinical management, though at present target therapies are not available, with the exception of the calcium sensing receptor agonists.

A diagnostic review of carcinomas and sarcomas of the mediastinum: making the diagnosis on fine-needle aspiration and core needle biopsy specimens

The mediastinum is a complex anatomic region that can pose many diagnostic challenges on fine-needle aspiration (FNA) and core needle biopsy (CNB). With the recent technological advancements in EBUS-TBNA and EUS-guided procedures, FNA/CNB is being increasingly utilized to obtain the initial and, in many cases, the only diagnosis. As a result, it is imperative to have an understanding of the pearls and pitfalls associated with both the more common and rarer malignancies that occur at this site. Although the vast majority of mediastinal malignancies encountered in routine clinical practice are metastatic carcinomas to mediastinal lymph nodes, primary tumors and tumors that directly extend into the mediastinum are also encountered. As always, a multimodal approach with clinical and radiographic correlation, a targeted IHC panel, and molecular testing when indicated are indisposable and necessary tools in the diagnostic workup of mediastinal malignancies. This review focuses on the salient diagnostic features of malignancies of epithelial and mesenchymal origin, excluding tumors of neurogenic, thymic, hematolymphoid, and germ cell origins, which are discussed in separate articles of this issue.

Benign lesions of the mediastinum: A review with emphasis on cytology and small biopsy specimens

This review focuses on the diagnosis of select benign processes, ranging from reactive entities to heterotopic tissues to neoplasms, which may occur in the mediastinum. Currently, the mediastinum can be evaluated and biopsied with endoscopic procedures. Therefore, cytopathology specimens, fine needle aspirations, and small biopsies play an important role in the diagnosis of these lesions. In this review, an emphasis is given to relevant clinical presentations, histologic and cytologic findings, differential diagnoses, ancillary testing, and interpretation. Pitfalls are reviewed and discussed in each section. It is important for both surgical pathologists and cytopathologists to be familiar with these entities and their cytologic and histologic features that may be helpful in reaching a diagnosis.