The oncocytic variant of papillary carcinoma of the thyroid: a clinicopathologic study of 15 cases

Oncocytic Follicular Cell-Derived Thyroid Tumors With Papillary Growth Pattern: A Clinicopathologic Study of 32 Cases

CONTEXT.—

Oncocytic thyroid tumors displaying a papillary growth pattern are rare and may cause diagnostic problems.

OBJECTIVE.—

To examine the clinicopathologic features of a series of 32 follicular cell-derived tumors composed of cells with oncocytic cytoplasm and displaying papillary architecture.

DESIGN.—

Thirty-two cases were collected and studied to assess clinicopathologic features, including immunohistochemical and molecular testing for BRAF V600E.

RESULTS.—

The patients were 26 women and 6 men, aged 17 to 77 years. The nodules ranged from 0.3 to 6.0 cm. Eighteen cases showed features of oncocytic hyperplastic nodules and were identified against a background of thyroid follicular nodular disease; 4 cases showed features of oncocytic follicular adenoma; and 10 cases corresponded to carcinomas with oncocytic and papillary features. Nuclear features of papillary thyroid carcinoma were absent or exceedingly rare. All cases were negative for HBME-1 and cytokeratin 19 (CK19) and wild type for BRAF V600E. Follow-up in 25 patients showed that all patients with hyperplastic nodules and oncocytic follicular adenomas were alive and well and free of disease from 7 to 20 years. One patient with oncocytic follicular carcinoma showed metastases and died of tumor at 16 months; 2 patients with carcinoma had metastases and recurrence at 6 and 7 years; and 5 patients with invasive tumors were free of disease from 5 to 10 years.

CONCLUSIONS.—

Oncocytic thyroid tumors with papillary features can span a spectrum from benign hyperplastic, to encapsulated neoplastic, to invasive malignant lesions. Owing to their papillary features, it is important not to confuse them for other types of thyroid tumors, such as oncocytic papillary thyroid carcinoma.

Encapsulated Papillary Oncocytic Neoplasm: A Newly Recognized Hurthle Cell Neoplasm With Unique Morphology

Diagnosis of oncocytic neoplasm of the thyroid gland can be challenging especially on fine needle aspiration biopsy (FNAB), given the wide differential diagnoses. In this report, we present the case of a 66-year-old male with an incidental thyroid nodule identified on imaging. In this case, identification of the distinctive cytologic features leads to the diagnosis of papillary oncocytic neoplasm on FNAB and helped to decide the appropriate surgical management. To date, the cytomorphologic features of this lesion are not well studied and established, with only a single case report in the literature. Herein, we describe the characteristic cytomorphologic and immunophenotypic features of this neoplasm. The recognition of the unique cytomorphologic features and awareness of the non-classic expression of the thyroid lineage markers will help in accurate diagnosis and management of this entity.

Overview of the 2022 WHO Classification of Thyroid Neoplasms

This review summarizes the changes in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors that relate to the thyroid gland. The new classification has divided thyroid tumors into several new categories that allow for a clearer understanding of the cell of origin, pathologic features (cytopathology and histopathology), molecular classification, and biological behavior. Follicular cell-derived tumors constitute the majority of thyroid neoplasms. In this new classification, they are divided into benign, low-risk, and malignant neoplasms. Benign tumors include not only follicular adenoma but also variants of adenoma that are of diagnostic and clinical significance, including the ones with papillary architecture, which are often hyperfunctional and oncocytic adenomas. For the first time, there is a detailed account of the multifocal hyperplastic/neoplastic lesions that commonly occur in the clinical setting of multinodular goiter; the term thyroid follicular nodular disease (FND) achieved consensus as the best to describe this enigmatic entity. Low-risk follicular cell-derived neoplasms include non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), thyroid tumors of uncertain malignant potential, and hyalinizing trabecular tumor. Malignant follicular cell-derived neoplasms are stratified based on molecular profiles and aggressiveness. Papillary thyroid carcinomas (PTCs), with many morphological subtypes, represent the BRAF-like malignancies, whereas invasive encapsulated follicular variant PTC and follicular thyroid carcinoma represent the RAS-like malignancies. This new classification requires detailed subtyping of papillary microcarcinomas similar to their counterparts that exceed 1.0 cm and recommends not designating them as a subtype of PTC. The criteria of the tall cell subtype of PTC have been revisited. Cribriform-morular thyroid carcinoma is no longer classified as a subtype of PTC. The term "Hürthle cell" is discouraged, since it is a misnomer. Oncocytic carcinoma is discussed as a distinct entity with the clear recognition that it refers to oncocytic follicular cell-derived neoplasms (composed of > 75% oncocytic cells) that lack characteristic nuclear features of PTC (those would be oncocytic PTCs) and high-grade features (necrosis and ≥ 5 mitoses per 2 mm²). High-grade follicular cell-derived malignancies now include both the traditional poorly differentiated carcinoma as well as high-grade differentiated thyroid carcinomas, since both are characterized by increased mitotic activity and tumor necrosis without anaplastic histology and clinically behave in a similar manner. Anaplastic thyroid carcinoma remains the most undifferentiated form; squamous cell carcinoma of the thyroid is now considered as a subtype of anaplastic carcinoma. Medullary thyroid carcinomas derived from thyroid C cells retain their distinct section, and there is a separate section for mixed tumors composed of both C cells and any follicular cell-derived malignancy. A grading system for medullary thyroid carcinomas is also introduced based on mitotic count, tumor necrosis, and Ki67 labeling index. A number of unusual neoplasms that occur in the thyroid have been placed into new sections based on their cytogenesis. Mucoepidermoid carcinoma and secretory carcinoma of the salivary gland type are now included in one section classified as "salivary gland-type carcinomas of the thyroid." Thymomas, thymic carcinomas and spindle epithelial tumor with thymus-like elements are classified as "thymic tumors within the thyroid." There remain several tumors whose cell lineage is unclear, and they are listed as such; these include sclerosing mucoepidermoid carcinoma with eosinophilia and cribriform-morular thyroid carcinoma. Another important addition is thyroblastoma, an unusual embryonal tumor associated with DICER1 mutations. As in all the WHO books in the 5th edition, mesenchymal and stromal tumors, hematolymphoid neoplasms, germ cell tumors, and metastatic malignancies are discussed separately. The current classification also emphasizes the value of biomarkers that may aid diagnosis and provide prognostic information.

Oncocytic Change in Thyroid Pathology

Oncocytes are cells that have abundant eosinophilic cytoplasm due to the accumulation of mitochondria; they are also known as oxyphils. In the thyroid they have been called Hürthle cells but this is a misnomer, since Hürthle described C cells; for this reason, we propose the use of "oncocyte" as a scientific term rather than an incorrect eponym. Oncocytic change occurs in nontumorous thyroid disorders, in benign and malignant tumors of thyroid follicular cells, in tumors composed of thyroid C cells, and intrathyroidal parathyroid proliferations as well as in metastatic lesions. The morphology of primary oncocytic thyroid tumors is similar to that of their non-oncocytic counterparts but also is complicated by the cytologic features of these cells that include both abundant eosinophilic cytoplasm and large cherry red nucleoli. The molecular alterations in oncocytic thyroid tumors echo those of their non-oncocytic counterparts but in addition feature mitochondrial DNA mutations as well as chromosomal gains and losses. In this review we emphasize the importance of recognition of the spectrum of oncocytic thyroid pathology. The cell of origin, morphologic features including architecture, nuclear atypia and invasive growth, as well as high grade features such as mitoses and necrosis, enable accurate classification of these lesions. The molecular alterations underlying the pathological entity are associated with genetic alterations associated with oncocytic change. The arbitrary cut-off of 75% oncocytic change to classify a lesion as an oncocytic variant brings another complexity to the classification scheme of tumors that frequently have mixed oncocytic and non-oncocytic components. This controversial and often confusing area of thyroid pathology requires thoughtful and cautious investigation to clarify accurate diagnosis, prognosis and prediction for patients with oncocytic thyroid lesions.

Clinicopathological features and outcomes after radioactive iodine treatment of oncocytic well-differentiated thyroid carcinomas

OBJECTIVE

The aim of this study was to compare the clinicopathological features of Hürthle cell carcinomas (HCC) and oncocytic papillary thyroid carcinomas (OPTC) and to evaluate their response to radioactive iodine (RAI) treatment.

METHODS

We retrospectively reviewed the charts of patients with histopathologically verified OPTC (group 1) and HCC (group 2), during a 17-year period. All patients underwent total thyroidectomy and received RAI adjuvant therapy. Clinicopathological characteristics of the two groups were compared. Response to initial therapy was assessed 6 to 24 months after RAI ablation according to the American Thyroid Association dynamic risk reclassification. Clinical outcomes were evaluated.

RESULTS

A total of 28 patients (8 OPTC and 20 HCC) were included. There was no significant difference in clinicopathological features including sex, age, tumour size and vascular invasion. Distant metastases were absent in both groups. OPTC, however, presented more features of local invasion (50% vs. 10%, P = 0.03), extrathyroidal extension (25% vs. 0%, P = 0.07) and lymph node involvement (37.5% vs. 0%, P = 0.01). Median cumulative RAI activity administered to both groups was 200 mCi (range: 100-300 mCi). Response to RAI therapy was excellent in all HCC and 87.5% of OPTC (P = 0.28). One patient with OPTC (12.5%) presented an indeterminate response. Clinical outcomes were favourable after a median follow-up of 87.5 and 49 months, respectively.

CONCLUSION

Although OPTC presented more locoregional invasion, clinicopathological characteristics of OPTC and HCC were comparable. Both OPTC and HCC were iodine responsive. We suggest that adjuvant RAI therapy after total thyroidectomy is beneficial for OPTC and HCC and may improve disease-free survival.

Patients with Oncocytic Variant Papillary Thyroid Carcinoma Have a Similar Prognosis to Matched Classical Papillary Thyroid Carcinoma Controls

BACKGROUND

Previous studies have suggested that oncocytic variant papillary thyroid carcinoma (PTC) may be more aggressive, with higher rates of recurrent disease. The aim of this study was to evaluate characteristics and outcomes of patients with oncocytic variant PTC compared to classical PTC.

METHODS

Patients with oncocytic variant PTC were retrospectively identified from 519 patients who underwent thyroidectomy for PTC between January 2009 and August 2015. Data collected included patient demographics, laboratory and pathology findings, imaging studies, treatment, and follow-up. Patients were matched 1:1 by age, sex, and TNM stage with patients who underwent total thyroidectomy for classical PTC during the same time period.

RESULTS

The cohort included 21 patients, of whom 18 (86%) were female, with a median age of 53 years (range 23-68 years). All patients underwent total thyroidectomy, and 17 (81%) had a central compartment neck dissection (8 [38%] prophylactic). The median tumor size was 2.0 cm (range 0.9-6.5 cm), and four (19%) patients had extrathyroidal extension. There was no significant difference in histopathologic characteristics, including extrathyroidal extension and lymphovascular invasion, between the two groups except for an increased incidence of thyroiditis in oncocytic variant PTC (90.5% vs. 57%; p = 0.01). In oncocytic variant PTC patients who underwent central compartment neck dissection, malignant lymph nodes were found in 12 (57%) patients compared to 13 (62%) classical (p = 0.75). Lateral neck dissection was performed in 5 (24%) oncocytic variant and classical PTC patients, with metastatic lymphadenopathy found in four (a median of four malignant lymph nodes; range 1-6) and five (a median of 2.5 malignant lymph nodes; range 1-9), respectively. Radioactive iodine was administered to 18 (86%) oncocytic variant PTC and 18 (86%) classical PTC patients. At a median follow-up of 51 months (interquartile range 38-61), one oncocytic variant PTC patient had recurrent disease and underwent reoperation at 24 months. In classical PTC patients with a median follow-up time of 77 months (range 56-87 months), two (9.5%) patients had detectable thyroglobulin levels indicating early recurrence, but neither has undergone reoperation.

CONCLUSIONS

Oncocytic variant PTC was present in 5% of PTC patients. Most (95%) patients remain disease-free at four years, similar to classical PTC outcomes, suggesting that oncocytic variant may not represent a more aggressive variant.

Hürthle Cell Carcinoma: Clinic-Pathological and Biological Aspects

Despite its structural simplicity the thyroid gland can give rise to a wide variety of tumor types.

Although a substantial amount of work has been done in the past twenty-five years to redefine the clinic-pathological features of most types of thyroid tumors of follicular cell origin, some aspects of thyroid tumors composed of oncocytes, generally known as Hürthle cell tumors, are still matter of discussion. The major issues concern their very existence as a bona fide tumor type, the occurrence of benign and malignant forms and their relative frequency, the predictive value of morphologic parameters, the natural history of the malignant forms and the classification of Hürthle cell tumors with a papillary growth pattern. The definition of oncocytic cell, oncocytic neoplasm and oncocytic carcinoma as well as the pathologic characteristics and clinical behavior of neoplasms composed of oncocytes will be discussed.

Metabolic Reprogramming in Thyroid Carcinoma

Among all the adaptations of cancer cells, their ability to change metabolism from the oxidative to the glycolytic phenotype is a hallmark called the Warburg effect. Studies on tumor metabolism show that improved glycolysis and glutaminolysis are necessary to maintain rapid cell proliferation, tumor progression, and resistance to cell death. Thyroid neoplasms are common endocrine tumors that are more prevalent in women and elderly individuals. The incidence of thyroid cancer has increased in the Past decades, and recent findings describing the metabolic profiles of thyroid tumors have emerged. Currently, several drugs are in development or clinical trials that target the altered metabolic pathways of tumors are undergoing. We present a review of the metabolic reprogramming in cancerous thyroid tissues with a focus on the factors that promote enhanced glycolysis and the possible identification of promising metabolic targets in thyroid cancer.

Pathologic Reporting of Tall-Cell Variant of Papillary Thyroid Cancer: Have We Reached a Consensus?

BACKGROUND

Tall-cell variant (TCV) is widely believed to be a more aggressive subtype of papillary thyroid carcinoma (PTC). Despite the significance of TCV with respect to risk stratification and therapeutic decision making, its diagnosis is subject to inter-observer variability. This study aimed to determine the level of agreement among expert pathologists in the identification and reporting of TCV.

METHODS

Seventeen surgical resections for thyroid cancer containing the diagnostic term "tall cell" in their pathology reports and 22 cases diagnosed as classical PTC were selected. Cases were digitalized, and 14 expert pathologists reviewed the scanned slides blinded to the original interpretation. Each pathologist designated each case as TCV or not and answered multiple questions about diagnostic histopathologic features of TCV.

RESULTS

The overall strength of agreement for identifying TCV was fair (Fleiss kappa 0.34), and the proportion of observed agreement was 0.70. Of 22 cases originally diagnosed as PTC classical variant, 15 (68%) were reclassified as TCV by at least one expert pathologist. It was noted that four different definitions for TCV were used by the participants based on various combinations of cell height to width (H:W) ratio and the percentage of tumor cells showing that specific ratio. All pathologists agreed that the diagnosis of TCV does not rely solely on a specific H:W ratio.

CONCLUSIONS

Pathologic reporting of TCV varies among pathologists. This disagreement is a result of the lack of unanimous diagnostic criteria and variation in individual pathologists' interpretations. These discrepancies lead to over- and under-diagnosis of TCV, which has significant implications in patient management. It is imperative to understand this variability in diagnosis TCV as it relates to risk stratification and interpretation of clinical studies related to this histologic subtype of PTC. Further studies are needed to reach consensus on the diagnostic criteria of TCV.

Genomic Hallmarks of Thyroid Neoplasia

The genomic landscape of thyroid cancers that are derived from follicular cells has been substantially elucidated through the coordinated application of high-throughput genomic technologies. Here, I review the common genetic alterations across the spectrum of thyroid neoplasia and present the resulting model of thyroid cancer initiation and progression. This model illustrates the striking correlation between tumor differentiation and overall somatic mutational burden, which also likely explains the highly variable clinical behavior and outcome of patients with thyroid cancers. These advances are yielding critical insights into thyroid cancer pathogenesis, which are being leveraged for the development of new diagnostic tools, prognostic and predictive biomarkers, and novel therapeutic approaches.

Oncogenes, mitochondrial metabolism, and quality control in differentiated thyroid cancer

Thyroid cancer is one of the most common malignancies of endocrine organs, and its incidence rate has increased steadily over the past several decades. Most differentiated thyroid tumors derived from thyroid epithelial cells exhibit slow-growing cancers, and patients with these tumors can achieve a good prognosis with surgical removal and radioiodine treatment. However, a small proportion of patients present with advanced thyroid cancer and are unusually resistant to current drug treatment modalities. Thyroid tumorigenesis is a complex process that is regulated by the activation of oncogenes, inactivation of tumor suppressors, and alterations in programmed cell death. Mitochondria play an essential role during tumor formation, progression, and metastasis of thyroid cancer. Recent studies have successfully observed the mitochondrial etiology of thyroid carcinogenesis. This review focuses on the recent progress in understanding the molecular mechanisms of thyroid cancer relating to altered mitochondrial metabolism.

Hürthle cell carcinoma: current perspectives

Hürthle cell carcinoma (HCC) can present either as a minimally invasive or as a widely invasive tumor. HCC generally has a more aggressive clinical behavior compared with the other differentiated thyroid cancers, and it is associated with a higher rate of distant metastases. Minimally invasive HCC demonstrates much less aggressive behavior; lesions <4 cm can be treated with thyroid lobectomy alone, and without radioactive iodine (RAI). HCC has been observed to be less iodine-avid compared with other differentiated thyroid cancers; however, recent data have demonstrated improved survival with RAI use in patients with HCC >2 cm and those with nodal and distant metastases. Patients with localized iodine-resistant disease who are not candidates for a wait-and-watch approach can be treated with localized therapies. Systemic therapy is reserved for patients with progressive, widely metastatic HCC.

Implications of oncocytic change in papillary thyroid cancer

OBJECTIVE

Although the presence of oncocytic change in less than 75% of a tumour is not considered to indicate oncocytic variants of papillary thyroid carcinoma (PTC), we frequently observe partial oncocytic change, especially in obese PTC patients. Thus, we sought to investigate the relationship between the presence of oncocytic change of PTC and its prognosis.

DESIGN, SETTING AND PARTICIPANTS

We retrospectively studied 142 patients with PTC who had undergone surgery between 2000 and 2005, and re-evaluated their PTC slides to record the proportion of oncocytic change in 10% increments from 0% to 100%.

MAJOR OUTCOME MEASURE

We analysed the relationship between the proportion of oncocytic change and clinicopathological prognostic factors.

RESULTS

Oncocytic change was found in 45·8% (65/142) of PTC patients. The proportion of patients with oncocytic change was higher in obese patients than in lean patients and showed a significant correlation with the BMI (r = 0·195, P = 0·020). The PTC patients with oncocytic change showed a higher recurrence rate than PTC patients without oncocytic change (30·8% vs 11·7%, respectively; P = 0·005). The presence of oncocytic change in PTC patients was associated with a shorter disease-free survival in a Kaplan-Meier analysis after a mean follow-up of 8·9 years.

CONCLUSION

The patients with PTC with oncocytic change presented with a higher recurrence rate and were more likely to be obese. These findings suggest that presence of oncocytic change is a poor prognostic factor in PTC patients, even if the oncocytic change involves less than 75% of a tumour.

Hurthle Cell Lesion: Controversies, Challenges, and Debates

Hurthle cell lesion is one of the most questionable clinico-pathological entities in most of its aspects. Literature has used the terms oncocytic, oxyphilic, Hurthle, and Ashkanazy interchangeably; what does each term denote? Who first described these cells? What is the cell of origin? How much Hurthle cells should be present to define the lesion as Hurthle cell one? Is it possible to differentiate hyperplastic from neoplastic and benign from malignant Hurthle cell lesion on a non-histopathologic ground? Does it belong to follicular or to papillary neoplasms or should it be classified separately? Can we anticipate its clinical behavior or predict its outcome? How can we manage? We will try to answer these questions in light of the ongoing relevant arguments with the aim of resolving some uncertainties and suggesting how to solve others.

Cytomorphologic features and ultrasonographic characteristics of thyroid nodules with Hurthle cells

This study was designed to evaluate the ultrasonographic and histopathologic features of nodules composed predominantly of Hurthle cells detected during cytological examination. Fifty-seven patients with thyroid nodules composed predominantly of Hurthle cells on fine needle aspiration cytology were retrospectively analyzed. Patients were evaluated by thyroid ultrasonography (US), and biopsy samples taken by US-guided fine needle aspiration cytology were assessed histopathologically. There were 57 patients and 57 nodules with Hurthle cells in cytological examination; 49 (86%) were classified as Bethesda 1, and 8 (14%) were classified as Bethesda 3. Histopathologically, 45 (78.9%) nodules were benign and 12 (21.1%) were malignant. Nuclear groove, transgressing blood vessel, and absence of colloid were observed with a higher frequency in malignant nodules compared to benign nodules (P < .05). There were no specific morphological features (nodule echogenity, presence of microcalsification, presence of cystic areas, absence of halo, margin irregularity, and increased blood flow) predicting malignancy in the US evaluation of nodules including Hurthle cells. Nuclear groove, transgressing blood vessel, and absence of colloid on cytomorphological evaluation are indicative of malignancy in nodules containing Hurthle cells.

Sonographic and cytopathologic correlation of papillary thyroid carcinoma variants

Papillary thyroid carcinoma (PTC) is the most common thyroid cancer and constitutes more than 70% of thyroid malignancies. Although TNM staging is the most widely used parameter for determination of therapeutic plans, recent studies have suggested that different histopathologic variants of PTC can also have different clinical courses and patient prognoses. Sonographic criteria for PTC are well established and include a taller-than-wide shape, an irregular margin, microcalcifications, and marked hypoechogenicity. The role of sonography has expanded to enable the characterization of PTC variants based on their sonographic features. Tall cell and diffuse sclerosing variants appear to have more aggressive clinical courses with unfavorable prognoses, whereas the more recently described cribriform-morular and Warthin-like variants have relatively indolent clinical courses. The prognoses of patients with follicular, solid, columnar cell, and oncocytic variants are still controversial and may be similar to the prognosis of conventional PTC. Understanding the sonographic characteristics of PTC variants with clinicopathologic correlation may be helpful for suggesting an appropriate treatment plan.

Expression patterns of glucose transporter-1 gene and thyroid specific genes in human papillary thyroid carcinoma

PURPOSE

The expression of glucose transporter-1 (Glut-1) gene and those of major thyroid-specific genes were examined in papillary carcinoma tissues, and the expressions of these genes were compared with cancer differentiation grades.

MATERIALS AND METHODS

Twenty-four human papillary carcinoma tissues were included in this study. The expressions of Glut-1- and thyroid-specific genes [sodium/iodide symporter (NIS), thyroid peroxidase, thyroglobulin, TSH receptor and pendrin] were analyzed by RT-PCR. Expression levels were expressed as ratios versus the expression of beta-actin. Pathologic differentiation of papillary carcinoma was classified into a relatively well-differentiated group (n = 13) and relatively less differentiated group (n = 11).

RESULTS

Glut-1 gene expression was significantly higher in the less differentiated group (0.66 ± 0.04) than in the well-differentiated group (0.59 ± 0.07). The expression levels of the NIS, PD and TG genes were significantly higher in the well-differentiated group (NIS: 0.67 ± 0.20, PD: 0.65 ± 0.21, TG: 0.74 ± 0.16) than in the less differentiated group (NIS: 0.36 ± 0.05, PD: 0.49 ± 0.08, TG: 0.60 ± 0.11), respectively. A significant negative correlation was found between Glut-1 and NIS expression, and positive correlations were found between NIS and TG, and between NIS and PD.

CONCLUSION

The NIS, PD and TG genes were highly expressed in well-differentiated thyroid carcinomas, whereas the Glut-1 gene was highly expressed in less differentiated thyroid carcinomas. These findings provide a molecular rationale for the management of papillary carcinoma, especially in the selection of FDG PET or radioiodine whole-body scan and I-131-based therapy.

Oncocytic lesions of the neuroendocrine system

This paper reviews the pathologic features of lesions which are oncocytic and involve classic endocrine organs. The history of the oncocytic cell, its morphologic and ultrastructural features, and important immunohistochemical findings are reviewed. Oncocytic proliferations including non-neoplastic and neoplastic of the thyroid, parathyroid, adrenal (both cortex and medulla), and pituitary are described. Their clinical relevance, functional capacity and capability, and where appropriate, prognostic implications are discussed. Important and relevant molecular biological information is included where appropriate.

Morphological difference in adult thyroid papillary carcinoma between Japan and Ukraine

Geographic differences have been reported to affect the morphological and molecular features of papillary thyroid carcinomas (PTCs). The area around Chernobyl is well-known to be iodine-deficient in contrast to Japan, an iodine-rich country. We reviewed histological differences in adult PTC between Ukraine and Japan. In total, 112 PTCs from age- and sex-matched adults (Ukraine 56, Japan 56) were evaluated histologically for several factors including tumor size, capsulation, tumor components (papillary, follicular, solid, trabecular), lymph node metastasis, extrathyroid invasion, lymphocytic infiltration, oxyphilic metaplasia, and MIB-1 index. We demonstrated that tumors were smaller (1.56 vs. 2.13 cm, p<0.05) and more solid and that lymph node metastasis was less frequent (14.3% vs. 48.2%, p<0.001) in Ukrainian cases. PTC subtype distribution was significantly different between the two groups. Solid variant (8.9% vs. 1.8%) and mixed subtypes with solid components were more frequent in Ukrainian patients. In contrast, classical papillary carcinomas were more frequent in Japanese cases (10.7% vs. 50.0%, p<0.001). Marked oxyphilic metaplasia was more common in Ukrainian cases (33.9 % vs. 8.9 %, p<0.001). MIB-1 index was significantly higher in Ukrainian cases (2.9% vs. 1.8%, p<0.001). However, the frequencies of tumor capsule formation and background lymphoid follicle formation around the tumor were similar between groups. Morphological differences in adult PTCs were similar to those in pediatric PTCs as reported previously, suggesting that morphogenesis of PTC is influenced by environmental factors, especially dietary iodine, as well as genetic factors.

Pathological characteristics and clinical perspectives of papillary thyroid cancer: study of 714 patients

Papillary thyroid cancer belongs to most commonly diagnosed well-differentiated malignant tumor of the thyroid gland, with only minority of cases being more aggressive, recurring locoregionally and developing distant metastatic foci. The aim of this study was to determine the clinical relationship between parameters of age, gender, size of primary tumor, intraglandular dissemination and regional metastatic spread and evaluate the importance of each parameter; analyze other major aggressive factors (tumor border, thyroid capsule invasion, perivascular, perilymphatic spread) on prevalence and extent of intraglandular dissemination and relation to metastatic spread in neck. This study is a retrospective analysis of clinical and pathological data from 714 patients with papillary thyroid cancer, presented and operated at the Department of ENT/Head and Neck surgery, Sisters of Charity University Hospital, Zagreb, in the period from 1980 to 2008. All patients were operated upon with total thyroidectomy and some type of neck lymphonode dissection (paratracheal or lateral). In results, we found 46.9% tumors were aggressive; 34.7% tumors were multicentric, with foci in the contralateral lobe nearly twice as often as in the ipsilateral lobe; 27.8% were regionally metastatic, with equal distribution between paratracheal and lateral regions. In conclusion, we revealed contralateral lobe multicentricity and male gender as independent risk factors for regional metastatic dissemination. Nodular goiter has been identified as a protective parameter.

Preoperative ultrasonographic features of papillary thyroid carcinoma predict biological behavior

BACKGROUND

Although ultrasound (US) features of papillary thyroid carcinoma (PTC) are well established, little is known regarding biological behavior according US features. We investigated whether there was a difference in biological behavior between PTCs that did and did not meet malignant US criteria.

PATIENTS AND METHODS

We retrospectively reviewed clinical records and histological and US findings of the index tumors in 488 patients who underwent surgery for PTC. Benign-looking PTC (B-PTC) was defined as showing none of the accepted US criteria for malignancy. Malignant-looking PTCs (M-PTCs) and B-PTCs were compared in terms of patients' age, sex, tumor size, histological subtype, multifocality, lymph node (LN) metastasis, extrathyroidal extension, stage, recurrence, and distant metastasis.

RESULTS

B-PTCs accounted for 74 (15%) of all 488 PTCs. Mean tumor size was not significantly different between the groups, with 1.10 cm for M-PTC and 1.11 cm for B-PTC (P = .947). Univariate and multivariate analysis indicated that M-PTC more frequently had LN metastasis, extrathyroidal extension, and a higher stage than B-PTC (all P < .05). The results were significant in tumors ≥1.0 cm, whereas there were no significant differences in tumors <1 cm. As the number of malignant US features increased, multifocality, extrathyroidal extension, LN metastasis, and a higher stage were more likely.

CONCLUSION

PTCs that did not meet malignant US criteria had better prognostic indicators than PTCs that met US criteria. Therefore, US features at the time of diagnosis can serve as a useful tool for predicting biological behavior in PTC.

Histological patterns of locoregional recurrence in Hürthle cell carcinoma of the thyroid gland

BACKGROUND

Hürthle cell carcinoma (HCC) is regarded as an aggressive variant of follicular thyroid carcinoma based in part on its propensity to metastasize regionally and recur locally. The current treatment recommendation of formal regional lymph node dissection is largely based on the presumption of lymphatic dissemination to cervical lymph nodes as the main mechanism of regional spread. The purpose of this study was to better define the distribution of locoregional recurrence in HCC, and specifically to differentiate soft-tissue implants from true nodal metastases.

METHODS

The surgical pathology files of The Johns Hopkins Hospital were searched for cases of HCC with locoregional recurrences. The slides were reviewed to assess the histologic patterns of tumor spread, including the presence or absence of lymph node metastasis. Elastic staining was used to confirm vessel invasion.

RESULTS

Twenty-four cases from 19 patients were identified. Thirteen were men, and the patients ranged in age from 35 to 83 years (mean 66). All had total or near-total thyroidectomies, and 16 received postoperative radioactive iodine. The time from primary diagnosis to first recurrence ranged from 0 to 12 years (mean 5 years). The locoregional disease involved the lateral neck (n=16), central neck (n=18), and larynx/trachea (n=4). In all 24 cases, the dominant tumor nodule was present as a rounded nodule of carcinoma within the soft tissues and unassociated with lymphoid tissue. Of 22 cases evaluated by elastic staining, 13 had tumor nodules within veins. True lymph node metastases were present in only six (25%) cases, and in all but one case, the lymph node metastases were <0.5 cm.

CONCLUSIONS

When HCC spreads in the neck, it usually does so as soft-tissue implants likely resulting from spread within venous channels. True lymph node metastases are not a major source of nodular recurrences in the neck. Resolving the pattern of tumor spread could help guide and refine the management of locoregional recurrence for patients with HCC.

Papillary thyroid carcinoma: differential diagnosis and prognostic values of its different variants: review of the literature

Papillary thyroid carcinoma is the most common thyroid malignancy, and has an excellent prognosis, even with cervical lymph node metastasis; however, histological variants are considered relevant, which may be associated with familial adenomatous polyposis and tumor aggressiveness. Histological features, such as vascular and/or lymphatic invasion, angiogenesis, multifocality, high cellular proliferation rate, neoplastic cell dissemination, and the histological varieties, are indicative of poor prognosis, together with associated clinical factors: age, sex, and tumor size.

Encapsulated papillary oncocytic neoplasms of the thyroid: morphologic, immunohistochemical, and molecular analysis of 18 cases

Encapsulated papillary oncocytic neoplasms (EPONs) of the thyroid are rare tumors, whose relationship to other thyroid tumors has not been thoroughly elucidated. Earlier, they have been regarded as variants of papillary thyroid carcinoma (PTC), hyperplastic lesions, and follicular neoplasms. Eighteen EPONs were retrieved from our surgical pathology files and reviewed for defining morphologic features. Cases having the typical nuclear features of PTC were excluded. Immunohistochemistry (IHC) for CK19, HBME1, and CD56 was carried out. Microdissection, polymerase chain reaction, and sequencing of exon 15 of the BRAF gene were completed. Cases were evaluated for rearranged in transformation/papillary thyroid carcinoma RET/PTC rearrangement by fluorescent in situ hybridization (FISH). The majority of the tumors exhibited a distinctive histologic appearance. They were composed of true papillae lined by a single layer of predominantly cuboidal cells with oncocytic cytoplasm; hobnailing was typically prominent. Three tumors showed taller cells with uniformly apical nuclei and no hobnailing. Ten of 18 cases showed vascular and/or capsular invasion; hence, if the diagnostic criteria used to evaluate follicular neoplasms are applied, more than half of the tumors would be considered minimally invasive carcinomas. No cases were immunoreactive with antibodies to HBME1, whereas only 1 of 13 was immunoreactive for CK19. Six of 7 interpretable cases were immunoreactive for CD56. No BRAF point mutations or RET/PTC rearrangements were identified in the examined cases. All patients were alive at the time of last follow-up and no locally recurrent disease had been reported; however, 1 case was remarkable for a lymph node metastasis. Our results confirm that EPONs are histologically, immunohistochemically, and molecularly distinct from papillary thyroid carcinoma and seem to be most related to follicular neoplasms.

Papillary carcinoma tall cell variant (TCV): a review

Tall cell variant of papillary thyroid carcinoma is an aggressive form of thyroid cancer with a significant mortality. This review describes the pathology of this variant, compares it to its pathologic mimics and discusses its clinical pathologic features. The literature on this tumor is reviewed. A brief discussion of molecular pathologic correlates is included.

Tall cell variant of papillary thyroid carcinoma: Its characteristic features demonstrated by fine-needle aspiration cytology and immunohistochemical study

Tall cell variant (TCV) of papillary thyroid carcinoma is a rare tumor, which is usually associated with poor outcome, and pathologists often face the dilemma of proper diagnosis of TCV, not only by cytology but also histology. To allow surgeons to determine aggressiveness of the tumor before operation, it is important for pathologists to detect tall cell features correctly by fine-needle aspiration cytology (FNAC). However, the current criteria and definition of TCV are still controversial and confounded by another problem, the differential diagnosis from poorly differentiated thyroid carcinoma (PDC).In this report, we describe two cases of TCV and present characteristic FNAC findings. The tumor cells had a peculiar shape, which included tall, columnar, and oxyphilic cytoplasm with "eccentric," basally located nuclei. We propose new terms for these cells, such as "tail-like cells" or "tadpole cells."In the surgically-resected specimens, both cases exhibited remarkable extrathyroidal invasion accompanying prominent vascular invasions. They showed high Ki-67 (MIB-1) labeling index by immunohistochemistry, which indicated a higher proliferation activity of TCV than conventional form of papillary thyroid carcinoma.Furthermore, we discuss in this report the problematic issue of differential diagnosis of TCV from PDC and oxyphilic papillary thyroid carcinoma.

Oncocytic variant of papillary thyroid carcinoma associated with Hashimoto's thyroiditis: a case report and review of the literature

Identification of Hürthle cells on fine-needle aspiration (FNA) of the thyroid leads to a wide differential diagnosis including benignand malignant entities. We report the cytological and histological findings of a patient with an oncocytic variant of papillary thyroid carcinoma (PTC) with concurrent Hashimoto's thyroiditis. FNA revealed a lymphoplasmacytic infiltrate with Hürthle cells demonstrating abnormal chromatin patterns, nuclear enlargement, pleomorphism, intranuclear cytoplasmic invaginations, and foci of papillary aggregates. Because of the degree of nuclear atypia and suspicion for concurrent papillary thyroid carcinoma, a total thyroidectomy was performed revealing a papillary arrangement of Hürthle cells with classic PTC nuclear changes and associated Hashimoto's thyroiditis. This report discusses cytopathological features of a rare variant of PTC (oncocytic subtype) in the background of Hashimoto's thyroiditis. We also briefly discuss the differential diagnosis and diagnostic pitfalls of Hürthle cell lesions, with a review of the literature.

Clinicopathologic Features and Outcome of the Oncocytic Variant of Papillary Thyroid Carcinoma

Objectives:

The purpose of this study was to define the clinicopathologic features and outcome of the oncocytic variant of papillary thyroid carcinoma (OVPTC) with a review of the literature.

Methods:

Twenty-three patients with OVPTC over a 10-year period were studied. Demographic, clinical, and histopathologic features and outcome data were analyzed retrospectively.

Results:

Seventeen women and 6 men, ages ranging from 20 to 76 years (95% confidence interval, 43.0 to 54.48), were studied. Cervical lymph node involvement was found in 43.4% of the patients. Most of the recurrences were associated with thyroid masses greater than 2 cm in diameter. Evaluation of the overall survival data by the Kaplan-Meier method revealed that most recurrences took place earlier than 30 months, and the majority of patients (74%) were well, with no evidence of disease, up to 78 months after the last treatment. All of the OVPTC cases presented as nonencapsulated tumors, and 78.2% demonstrated extrathyroid stromal invasion.

Conclusions:

OVPTC is a unique variant of papillary thyroid carcinoma that has distinctive clinicopathologic features. Since OVPTC is often associated with local invasion and may involve cervical lymph nodes, it may require more extensive surgery than classic papillary thyroid carcinoma.

The Thyroid Hürthle (Oncocytic) Cell and Its Associated Pathologic Conditions: A Surgical Pathology and Cytopathology Review

Context.—Hürthle cells are eosinophilic, follicular-derived cells that are associated with a variety of nonneoplastic and neoplastic thyroid lesions. The differential diagnosis of Hürthle cell lesions is quite broad.

Objective.—To review the pathologic conditions associated with Hürthle cells in the thyroid and to discuss pathology of thyroid lesions associated with oncocytic cytology.

Data Sources.—A variety of thyroid nonneoplastic (autoimmune thyroiditis, multinodular goiter) and neoplastic conditions (Hürthle cell adenoma, Hürthle cell carcinoma) are associated with Hürthle cell cytology. In addition, there are several thyroid neoplasms that should be considered when one observes a Hürthle cell neoplasm in the thyroid (oncocytic variant of medullary carcinoma, several variants of papillary thyroid carcinoma).

Conclusions.—Oncocytic cytology is seen in a variety of thyroid conditions that are associated with a broad differential diagnosis and care must be used for accurate diagnosis. Newer molecular-based techniques may be useful for further classification of thyroid neoplasms with oncocytic pathology.

Prevalence and prognostic significance of tall cell variant of papillary thyroid carcinoma

The aim of this study was to assess the prevalence, prognostic factors, and long-term outcome of tall cell variant (TCV) in comparison with the conventional forms of papillary thyroid carcinoma (PTC). A total of 945 patients with thyroid cancer were treated and followed up from 1960 to 1998. Pathologic review was performed in 778 patients (84%) of the cohort. Of these, 674 had PTC: 503 (74%) had conventional form (CF); 56 (8%), TCV; and 155 (17%), other variants of PTC. Tall cell variant was associated with tumors of larger size (P < .001), bilaterality (P < .02), multifocality (P < .04), and extrathyroidal invasion (P < .001). Treatment was similar in both groups, but neck dissection was performed more frequently in patients with TCV (P < .04). The 10-year overall and event-free survival rates were, respectively, 90% and 85% in the CF versus 79% and 67% in the TCV group (P < .001). Histologic subtype did not have an effect on clinical outcome after multivariate analysis, the most relevant factors being age, involved nodes, or the "Metastasis, Age, Completeness, Invasion, Size" classification after multivariate analysis. In this large cohort of patients, TCV represents 8.3% of PTC, and it is a more aggressive form of PTC than CF because of the higher stage and increased grade.

A novel tumor marker, Niban, is expressed in subsets of thyroid tumors and Hashimoto's thyroiditis

Niban is a recently identified molecular marker of renal carcinogenesis in the Tsc2 gene-mutant Eker rat. Niban expression is most dramatically increased in the early stage of renal carcinogenesis and might decline during malignant progression. Niban is also expressed in various histologic types of human renal cell carcinoma. Therefore, Niban might be a good marker for renal carcinogenesis in both animal models and humans. In the present study, we examined Niban expression in various thyroid lesions by immunohistochemical staining using polyclonal rabbit antihuman Niban antibody. Normal thyroid tissue never stained for Niban. Niban was most frequently expressed in tumors with oxyphilic cytoplasm, including oxyphilic variants of papillary carcinoma (4/4 = 100%), oxyphilic variants of follicular adenoma (7/7 = 100%), and oxyphilic variants of follicular carcinoma (5/5 = 100%). Eighty-one percent (44/54) of papillary carcinoma cases, including microcarcinomas, and follicular variants were also positively stained for Niban at variable intensities. Follicular carcinomas were less frequently and less intensely stained. In nonneoplastic lesions, cells were rarely positively stained. In Hashimoto's thyroiditis, scattered cells with oxyphilic cell metaplasia were weakly Niban-positive. Reverse transcriptase-polymerase chain reaction and Western blot analysis of frozen tissue confirmed Niban expression at the molecular level in 4 cases of papillary carcinoma. Taken together, Niban expression is up-regulated in various types of thyroid tumors. We postulate that Niban expression may play an important role in the tumorigenic process of the thyroid in several scenarios. (1) Niban expression may be closely related to the carcinogenic process, especially from the early stage of papillary thyroid carcinoma. (2) Niban may be closely associated with altered mitochondrial functions in preneoplastic and neoplastic processes of the thyroid. (3) Niban may be a molecular marker of the oxyphilic phenotype under various conditions. Further functional studies of Niban will clarify the role of Niban in various thyroid lesions.

How to define follicular thyroid carcinoma?

The appropriate diagnosis of follicular thyroid carcinoma (FTC) still depends on its histological discrimination from follicular adenoma (including the distinction of benign from malignant oncocytic variants), papillary thyroid carcinoma (particularly from the follicular variants) and poorly differentiated thyroid carcinoma. The use of immunohistochemical markers contributed only marginally to better defining FTC. The introduction of the micro array technique, however, may offer the possibility of getting a better insight into the natural history, as well as predicting the clinical course, of a given thyroid nodule. This review attempts to recapitulate common standards in the diagnosis of FTC, to summarise current molecular data available to distinguish FTC from other benign and malignant tumours and, finally, to outline future perspectives to define FTC on its specific genetic features.

Aggressiveness of therapy and prognosis of patients with Hürthle cell papillary thyroid carcinoma

Hürthle cell papillary thyroid carcinoma (HCPTC) has been studied separately from other types of thyroid carcinoma in relatively few studies. The aim of our study was to determine the factors associated with the survival of patients with HCPTC in Slovenia, an iodine-deficient region. A total of 1552 patients with thyroid carcinoma were seen at our institute during the period of 1976-2003; of them, 42 patients (33 females, 9 males; age 10-85 years, median 56.5 years) had histopathologically verified HCPTC. The data on the patients' gender, age, disease history, extent of disease, morphologic characteristics, therapy, locoregional control, disease-free interval, and survival were collected. The statistical correlation between possible prognostic factors and the disease-free interval and survival was analyzed by chi2 test and log rank analysis. The tumor diameter ranged from 1 to 9 cm (median, 3 cm). Extrathyroid tumor growth was found in 19 patients, lymph node metastases in 13 patients, and distant metastases in 2 patients. Primary treatment consisted of total or near-total thyroidectomy (39 patients), lobectomy (2 patients), radioiodine ablation of the thyroid remnant (37 patients), external irradiation (14 patients), and chemotherapy (3 patients). Locoregional recurrence was diagnosed in four patients, and dissemination in 1 patient during the follow-up period of 0.75-20 years (median, 5.5 years). Three patients died of thyroid carcinoma during the follow-up period. The 5-year and 10-year survivals were 94% and 87%, respectively. The 5-year and 10-year disease-free intervals were 93% and 81%, respectively. The factors correlated with the survival were: age, extrathyroid tumor growth, primary tumor stage, and regional and distant metastases. Although extrathyroidal tumor growth was found in 45% of the patients with HCPTC, our patients had a favorable prognosis. Long-term survival and locoregional control of disease are likely after the radical tumor resection, radioiodine ablation of the thyroid remnant, and external irradiation.

The many faces and mimics of papillary thyroid carcinoma

This article provides an overview of the 15 histologic variants of papillary thyroid carcinoma listed by the 2004 World Health Organization (WHO) monograph on endocrine tumors. The histologic features, differential diagnosis, and clinical course of each variant are discussed in some detail. The follicular variants (conventional and macrofollicular) constitute a morphologic challenge because the majority of these tumors are encapsulated and, also, because, in many tumors, not all neoplastic cells show the nuclear features considered to be diagnostic of papillary carcinoma. As a result, most of these tumors are missed even by experienced pathologists. Moreover, hyperplastic thyroid lesions, follicular adenomas, and Hashimoto's thyroiditis may contain cells with clear nuclei resembling those of papillary carcinoma. Papillary carcinomas composed entirely of hyperchromatic cells have been overlooked. The WHO monograph defines papillary carcinoma with focal spindle and giant cell carcinoma components but its clinical behavior is unknown. Papillary carcinoma with an insular pattern that does not show the artifactual separation of the cell nests has been misinterpreted as the solid variant of papillary carcinoma. Papillary microcarcinomas include not only the conventional type and the follicular variants but also the tall cell and columnar cell variants.

Benign Hürthle cell adenoma with papillary architecture: a benign lesion mimicking oncocytic papillary carcinoma

We studied the significance of encapsulated Hürthle cell thyroid nodules with papillary structures lacking the nuclear features of papillary thyroid carcinoma (PTC); 19 cases fulfilling these criteria were encountered The patients' ages ranged from 22 to 40 years (32+/-6), and the F:M ratio was 3:1 The tumors measured from 0.5-5 cm (2+/-1.1). The diameter of the tumor cell nuclei ranged from 5.6 to 7.2 microns. Many nodules had nuclei displaying a fine chromatin pattern somewhat resembling those of PTC, but these were present in <20% of the tumor cells. Immunohistochemically, there was reactivity for MIB-1 in the papillary structures, negativity to focally weak reactivity for HBME and galectin-3, and negativity to moderate diffuse reactivity for CK19. Clinical follow-up from 1 to 19 years revealed no evidence of metastases in any of the cases. It is unlikely that the papillary structures in the study cases represent degenerative changes in view of the proliferative activity we have demonstrated in them. In view of (1) the encapsulation and the uniformity of the constituent cells, (2) the negative or weak immunoreactivity for galectin-3 and HBME and negative to moderate immunoreactivity for CK19, and (3) the absence or paucity of nuclear criteria for the diagnosis of PTC and the absence of lymph node metastasis in all study cases, we believe that these lesions represent the papillary variant of oncocytic follicular adenoma (Hürthle cell adenoma). Recognition of this entity is important to avoid an overdiagnosis of oncocytic PTC.

Pathologic Study and Clinical Significance of Hürthle Cell Papillary Thyroid Carcinoma

Hürthle cell papillary thyroid carcinoma is a variant of papillary thyroid carcinoma (PTC). Its pathologic and clinical significance has not been well documented. The authors studied the relative incidence of Hürthle cell PTC and the relationship of Hürthle cell PTC to other variants of thyroid carcinoma. Three hundred eighty consecutive cases of thyroid carcinoma were reviewed to identify cases with focal or extensive areas of Hürthle cell PTC, classic PTC, Hürthle cell carcinoma (ie, non-Hürthle cell PTC), and follicular carcinoma. In addition, the status of lymphoid infiltrate in the tumor, stromal invasion with desmoplastic reaction, vascular invasion, and distant and lymph node metastasis were noted by microscopic examination, review of clinical charts, or both. A total of 24 (HCs) and 42 PTCs with Hürthle cells were identified. The latter category was divided into pure Hürthle cell PTC or extensive Hürthle cell (HPTC) (28 cases) and PTC or Hürthle cell carcinoma with focal areas of Hürthle cell PTC (14 cases). The Hürthle cell PTC/Hürthle cell carcinoma ratio was lower than that of PTC/follicular carcinoma (39:289) (P = 0.001). Follicular or solid structures were present in all HPTCs. HPTCs were associated with frequent stromal intrathyroid and extrathyroid invasion, but they tended to have a lower rate of lymph node metastasis (8/28) compared with classic PTC with stromal invasion (108:200) (P = 0.12) and a lower rate of distant metastasis (2:28) compared with Hürthle cell carcinoma (15:24) (P = 0.02) or follicular carcinoma (13:39) (P = 0.04). Warthin-like Hürthle cell PTC (10 cases) was associated with extrathyroid invasion in five cases. In Hürthle cell PTC associated with tall cell variant (10 cases), areas of gradual transition between Hürthle cell PTC and tall cell variant were identified. The latter variant showed the highest rate of extrathyroid stromal and vascular invasion with distant metastasis and patient death compared with all Hürthle cell PTCs and classic PTCs. In conclusion, Hürthle cell PTC is frequently associated with tall cell variant. It has a higher potential for extrathyroid invasion than classic PTC and has vascular invasion and distant metastasis characteristics intermediate between those of classic PTC and Hürthle cell carcinoma with or follicular carcinoma. Hürthle cell PTC tends to show a greater likelihood of extrathyroid invasion when associated with Warthin-like features and tall cell variant PTC, and higher vascular invasion and distant metastasis when associated with tall cell variant.

Role of Fine-needle Aspiration Biopsy and Frozen Section in the Management of Papillary Thyroid Carcinoma Subtypes

Since fine-needle aspiration biopsy (FNAB) was introduced, the value of frozen section (FS) has been questioned. This study compares FNAB and FS sensitivities among the usual form of papillary thyroid cancer (uPTC) and variants of PTC such as tall cell (tcPTC), follicular (fPTC), and Hurthle cell (HcPTC). A total of 257 patients who underwent preoperative FNAB, intraoperative FS, and thyroidectomy for PTC were, randomly selected from a database of a university teaching hospital in Toronto. There were 218 females (84.8%) and 39 males (15.2%), from 19 to 89 years of age (mean of 44 years), having uPTC (n = 212), fPTC (n = 24), HcPTC (n = 14), and tcPTC (n = 7). Data were analyzed using chi2 test. Sensitivities were calculated by division of true positives and by the sum of true positives and false negatives. True positives had to reflect a conclusive diagnosis of cancer. The FNAB sensitivities were uPTC (39.2%), fPTC (25%), HcPTC (42.9%), tcPTC (85.7%), similar to FS sensitivities (p = 0.497) for uPTC (44.3%), fPTC (16.7%), HcPTC (42.9%), and tcPTC (71.4%). Use of FS following FNAB increased sensitivities for uPTC to 56.1%, fPTC to 29.2%, and tcPTC to 100%. In addition, FS did not increase FNAB sensitivity in HcPTC. Combination FNAB plus FS failed in 43.9% of uPTC, 70.8% of fPTC, and 57.1% of HcPTC. We concluded that FNAB and FS sensitivity vary with PTC subtype and are still necessary for selection and treatment. The recognition of morphologic subtypes of PTC from the FNAB could optimize the selection of patients for intraoperative FS, enhance the preoperative assessment of prognosis, facilitate the surgical planning, and simplify the preparation of postoperative adjuvant therapy.

The meaning and predictivity of Hürthle cells in fine needle aspiration cytology for thyroid nodular disease

AIMS

The significance of Hürthle cells in thyroid nodule fine needle aspiration cytology (FNAC) samples remains uncertain. This study aims to clarify the meaning and the predictivity of this kind of cells.

METHODS

One hundred and ten patients with Hürthle cells in FNAC of thyroid nodules were reviewed. Histopathology was correlated with cytological findings.

RESULTS

The density of Hürthle cells in FNACs ranged from 20 to 100%. Eighty-nine patients had benign nodular disease (Hürthle cell or follicular adenoma), and 21 patients had malignant tumours. The presence of more than 50% Hürthle cells in FNAC correlated with benign or malignant Hürthle cell neoplasm. Hürthle cell carcinomas displayed more than 90% Hürthle cells in FNAC.

CONCLUSIONS

Surgery is indicated for all nodular lesions with more than 50% Hürthle cells in FNAC.

Hürthle cell carcinoma: diagnostic and therapeutic implications

Background

Hürthle cell carcinoma is a variant of follicular cell carcinoma of thyroid. It may present as a low-grade tumour or as a more aggressive type. Prognosis depends upon the age of the patient, tumour size, extent of invasion and initial nodal or distant metastasis.

Patient and methods

The case of Hürthle cell carcinoma is reported in a 79-year-old man who presented with a rapidly increasing lump on the left side of his neck, having had a right hemithyroidectomy for colloid goitre 24-years-ago. Fine needle aspiration cytology confirmed the presence of Hürthle cells, raising the possibility of a Hürthle cell neoplasm. The patient underwent staging and surgery. Histology showed Hürthle cell carcinoma and the patient underwent adjuvant therapy. The literature on Hürthle cell neoplasms is reviewed.

Conclusions

Fine needle aspiration cytology may recognise Hürthle cell lesion but final diagnosis of carcinoma depends upon histological confirmation of vascular or capsular invasion. Staging and surgery in Hürthle cell carcinoma are similar to follicular carcinoma of thyroid with favourable outcome despite the controversy regarding the histological classification and adjuvant therapy. Elderly patients with Hürthle cell carcinoma need to be made aware of their poorer prognosis and should be offered more radical treatment.

Ultrastructural localization of thyroid peroxidase, hydrogen peroxide-generating sites, and monoamine oxidase in benign and malignant thyroid diseases

Despite thyroid tissue heterogeneity, biochemical and morphological features have been associated with certain thyroid diseases. We analyzed the ultracytochemical localization of thyroperoxidase (TPO), TPO-associated hydrogen peroxide-generating sites (H(2)O(2) sites), and monoamine oxidase (MAO) in terms of morphology and biochemical TPO activity in abnormal thyroids. We examined 11 cases of nontoxic multinodular goiter, 5 cases of Hashimoto's thyroiditis, 1 case of oncocytic (Hürthle or oxyphilic cell) adenoma, 5 cases of Graves' disease, 4 cases of papillary carcinoma, and 4 cases of perinodular normal tissue. In the perinodular tissue, TPO was detected mainly in the nuclear envelope, rough endoplasmic reticulum (RER), and subapical vesicles, but not in the apical surface. In multinodular goiter, heterogeneous TPO reactivity ranging from almost null to strongly positive was detected in similar locations as in the perinodular tissue, and was absent in the microvilli. Follicular cells from Hashimoto's thyroiditis displayed TPO in the nuclear envelope and the scarce RER. Remarkably, oncocytic cells from both Hashimoto's thyroiditis and oncocytic adenoma, typically packed with mitochondria, displayed evident TPO reaction exclusively in mitochondrial cristae. In Graves' disease, the nuclear envelope, enlarged RER, and apical vesicles were strongly TPO positive, and microvilli also exhibited TPO activity. Papillary carcinoma cells were negative for TPO. The localization and characteristics of TPO activity in the H(2)O(2) sites were similar to that of TPO in all tissues. MAO was positive in mitochondria of perinodular tissues, multinodular goiter, and oncocytes and negative in Hashimoto's thyroiditis and Graves' disease. Interestingly, MAO was intensely positive in the nuclear envelope of papillary carcinoma but unreactive in mitochondria. Biochemical TPO activity was increased in multinodular goiter and Graves' disease. In conclusion, several changes in ultracytochemical characteristics of TPO, H(2)O(2) sites, and MAO were associated with thyroid disease. Nonmalignant oncocytic cells exhibited an unusual mitochondrial location of TPO and H(2)O(2) sites. The distribution of MAO in nuclear envelope of papillary carcinoma cells could be a further feature of malignancy.

My approach to oncocytic tumours of the thyroid

The traditional approach to oncocytic thyroid lesions classified these as a separate entity, and applied criteria that are somewhat similar to those used for follicular lesions of the thyroid. In general, the guidelines to distinguish hyperplasia from neoplasia, and benign from malignant were crude and unsubstantiated by scientific evidence. In fact, there is no basis to separate oncocytic lesions from other classifications of thyroid pathology. The factors that result in mitochondrial accumulation are largely unrelated to the genetic events that result in proliferation and neoplastic transformation of thyroid follicular epithelial cells. The concept of classifying oncocytic lesions, including follicular variant papillary carcinomas, based on nuclear morphology, immunohistochemical profiles, and molecular markers may pave the way for a better understanding of the biology of oncocytic lesions of the thyroid.

The phenotype of Hurthle and Warthin-like papillary thyroid carcinomas is distinct from classic papillary carcinoma as to the expression of retinoblastoma protein and E2F-1 transcription factor

Retinoblastoma protein plays an important role in controlling cell cycle progression. The active form of retinoblastoma protein binds to E2F-1 and inhibits transcription of S phase genes. Overexpression of E2F-1 has been suggested as an important factor in carcinogenesis. The Hurthle cell (HPCA) and Warthin-like (WLPCA) variants of papillary carcinoma are two closely related entities that arise in association with Hashimoto's thyroiditis and share the presence of oxyphilic changes in the lining of epithelial cells and the presence of papillary nuclear features. The current study included formalin-fixed, paraffin-embedded tissues from 58 cases of thyroid papillary carcinoma: 20 HPCA, 6 WLPCA, 22 conventional papillary carcinomas (PCA), and 10 follicular variants of papillary carcinoma (FVPCA). The immunohistochemical studies were performed for retinoblastoma (Rb-1) and E2F-1, (KH95) after heat-induced epitope retrieval. None of the PCA or FVPCA cases were in the positive range for Rb-1. All cases of HPCA and WLPCA of the thyroid showed reactivity in 50% or more of the nuclei in the neoplastic cell population. As for E2F-1, all cases of HPCA and WLPCA showed positive reactivity, whereas none of the PCA or FVPCA cases were in the positive range. In conclusion, HPCA and WLPCA are Rb-positive and E2F-1-positive; PCA and FVPCA are Rb-negative and E2F1-negative. Hurthle metaplastic epithelium in Hashimoto's thyroiditis is Rb-positive and E2F-1-negative. This phenotypic difference is also helpful in distinguishing hyperplastic Hurthle cell proliferation in Hashimoto's thyroiditis from HPCA or WLPCA.

Hybrid thyroid carcinoma with a coarse chromatin pattern and nuclear features of papillary thyroid carcinoma

Hybrid follicular carcinoma (FC) and papillary thyroid carcinoma (PTC) have not been previously well described. Consecutive cases of 29 FC, 12 Hurthle cell carcinomas (HC), 247 PTC and 13 Hurthle cell PTC (HPTC) were reviewed with special attention to the coarse (CC) and fine chromatin patterns (FIC), as well as to the presence of nuclear grooves, pseudoinclusions or optically clear appearance. Limited nuclear features of PTC (LNF-PTC) are defined as areas of tumor with FIC in addition to some other nuclear features, but insufficient for the diagnosis of PTC. Tumors with nuclei showing an admixture of CC and PTC or LNFPTC were submitted for immunostaining for cytokeratin 19, HBME and Ret/PTC. FC and HC contained areas of LNFPTC in 25 tumors and focal PTC in 3 tumors. None of these cases was associated with lymph node metastasis. Areas with CC were found in 54 PTC and 3 HPTC. The rates of vascular invasion and distant metastasis tended to be higher for PTC with areas of coarse chromatin pattern than for PTC without such areas; however, the difference was not statistically significant. Immunoreactivity for cytokeratin 19 and HBME was moderate to strong for PTC and focal areas of PTC or LNFPTC in FC without Hurthle cell changes. Ret/PTC immunostaining was positive in areas of LNFPTC or focal PTC in three FC. Focal PTC or areas of LNFPTC are frequently seen in FC. Likewise, areas of CC are often present in PTC. The presence of these focal areas does not appear to change the clinical behavior of the tumor and therefore does not warrant a change of nomenclature.

Interpretation of RET immunostaining in follicular lesions of the thyroid

We applied monoclonal antibodies against RET and cytokeratin 19 (CK19) to the following tumor sections: classic papillary carcinoma (PC), 16; Hürthle-type PC (HPC), 1; sclerosing PC with nodular fasciitis-like stroma (SPC), 1; PC, follicular variant (FVPC), 12; follicular adenoma (FA), 9; Hürthle cell adenoma (HA), 4; Hürthle cell carcinoma (HC), 3; and follicular carcinoma (FC), 7. CK19+ tumors included 16 PCs, 1HPC, 1SPC, 11 FVPCs, 7 FAs, 4 FCs, and 1HC. RET+ tumors included 4 HAs, 3 HCs, 1HPC, 12 PCs, 7 FVPCs, and 2 FAs. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed a RET transcript in 6 Hürthle cell lesions. RET immunoreactivity is less sensitive and specific for PC than CK19. CK19 is useful for identifying PC, although only lesions with diffuse, intense staining should be considered positive. The detection of RET protein by immunohistochemical analysis was corroborated by the presence of the RET transcript by RT-PCR. Further study is warranted to determine whether this represents activation by gene fusion or some other mechanism in this subset of thyroid neoplasms.