TTF-1 Expression in Ovarian and Uterine Epithelial Neoplasia and its Potential Significance, an Immunohistochemical Assessment With Multiple Monoclonal Antibodies and Different Secondary Detection Systems:

Napsin-A Expression in Mesonephric and Mesonephric-like Adenocarcinomas: Implications for Distinction From Clear Cell Carcinoma

Mesonephric adenocarcinoma (MA) and mesonephric-like adenocarcinoma (MLA) are rare gynecological neoplasms that sometimes exhibit morphologic overlap with clear cell carcinoma (CCC), which may lead to diagnostic challenges. Napsin-A is regarded as the most specific immunohistochemical marker of CCC, but its expression in MLA and MA has not been widely investigated. This study investigated the expression of Napsin-A in a series of MAs and MLAs to determine its utility in distinguishing these neoplasms from CCC. The cohort included 32 MLAs arising in the ovary, endometrium, abdominal wall, and sigmoid mesocolon, 13 cervical MLAs, 2 ovarian mesonephric-like carcinosarcomas, and 1 cervical mesonephric carcinosarcoma, with Napsin-A immunohistochemistry performed on whole-slide tissue sections. Napsin-A staining was positive in 17 of 48 cases (35.4%), with focal granular cytoplasmic expression ranging from 1% to 40%. In all, 13/32 (40.6%) MLAs, 2/13 (15.4%) MAs, and 2/3 (66.7%) mesonephric or mesonephric-like carcinosarcomas were positive. Our results demonstrate that Napsin-A is expressed in a significant subset of MLAs and MAs. Given the morphologic and immunohistochemical overlap, this may contribute to misclassification as CCC, especially in cases with ambiguous morphology. Pathologists should be aware of this diagnostic pitfall and employ a panel of markers rather than relying on a single marker.

Clinicopathological and imaging features of struma ovarii: a retrospective study

Objectives

The struma ovarii (SO) is a rare disease, presenting significant challenges in achieving an accurate diagnosis. This study aims to delineate the clinicopathological and multimodal imaging characteristics of SO, enabling the precise diagnosis of this entity.

Methods

A retrospective analysis was conducted of the clinicopathological manifestations, laboratory examination results, and imaging data (including ultrasound and MRI) of 40 SO patients who received treatment at the First Affiliated Hospital of Ningbo University over the period from January 2010 to February 2024.

Results

The pathological results of 40 patients showed 21 pure SO, including 20 benign and one malignant; 19 patients had mixed SO, composed of 17 benign and two malignant. Three malignant cases were thyroid carcinoid. According to the ultrasound image, 40 SO patients were divided into three types: 22 cases were cystic, which had mainly single room or separations; 12 cases were mainly cystic-solid mixed, which had multiple septations and hyperechoic nodules; and six solid cases showed regular or irregular mass and rich blood supply. Five patients underwent contrast-enhanced ultrasound (CEUS) examination. The cystic wall and septation showed equal enhancement and slow regression. Two patients showed low enhancement in the protrusion and with slow regression. The MRI manifestations of SO are various. In this cohort, T1-weighted imaging (T1WI) showed hypo-intensity in six cases and heterogeneity in six cases; T2-weighted imaging (T2WI) showed hypo-intensity in two cases, heterogeneity in five cases, and hyper-intensity in four cases; diffusion-weighted imaging (DWI) showed hypo-intensity in two cases, heterogeneity in three cases, and hyper-intensity in four cases.

Conclusions

The incidence of SO is low, but there are some features in imaging. There were cystic, cystic-solid, or solid lesions in the appendage area; CEUS showed separations and solid components with rich blood flow and slow enhancement; MRI showed high signal on T2WI and multiple cysts and heterogeneous signal on T1WI, which were the imaging markers for SO. A comprehensive understanding of imaging manifestations can help radiologists identify this disease and provide a basis for an appropriate therapeutic regime.

Ovarian mucinous tumors do not usually harbor a mesonephric-like component

BACKGROUND

The origin of primary mucinous ovarian tumors remains uncertain. Recently, a number of published cases suggested a possible mesonephric origin. The aim of this study is to investigate the association between these two types of proliferation and to determine whether the theory regarding this origin of ovarian mucinous tumors could be further supported.

MATERIAL AND METHODS

In our retrospective study, we included 406 patients diagnosed with a primary ovarian mucinous tumor. Clinical parameters were extracted from the patients' files. The slides were reexamined to identify any potential mesonephric-like elements. Foci harboring characteristics suggestive of a mesonephric-like component were subjected to an immunohistochemical analysis with GATA3 (Eurobio, L50-823) and TTF-1 (Dako-Agilent, clone 8G7G3/1) antibodies.

RESULTS

The mean age at diagnosis was 47.4 years (range 6-94 years). The tumors (n = 417, 15 bilateral cases) were mucinous cystadenomas/cystadenofibromas (n = 305), borderline mucinous tumors (n = 84) and mucinous carcinomas (n = 28). Associated Brenner tumors were present in 16 cases and teratomas in 8 cases. Morphological analysis revealed 64 cases with a component that could be considered mesonephric-like. Two of these were TTF-1 positive and one of them expressed GATA3 weakly and very focally. However, these were interpreted as non-specific of mesonephric differentiation.

CONCLUSION

Our series of 417 ovarian mucinous tumors revealed no associated mesonephric-like components. To date, only eight mucinous tumors associated with mesonephric-like foci have been reported in the literature. Our results indicate that the association between these two types of tissue is probably too rare to imply a potential role in their histogenesis.

A Rare Case of Metachronous Clear Cell Ovarian Carcinoma and Thyroid Carcinoma: Clinical and Pathological Insights

Background

Clear cell ovarian carcinoma (CCOC) is a type of epithelial ovarian cancer, representing 5-11% of ovarian cancers. CCOCs tend to occur in the fifth to seventh decades of life, with only 10% of cases occurring in the fourth decade. On the other side, papillary thyroid carcinoma is the most common histology type of thyroid carcinoma and is associated with locoregional spread. Herein, we present a rare case of double-primer ovarian and thyroid cancer, which is a clear cell ovarian carcinoma metachronous with papillary thyroid carcinoma.

Case Report

A 47-year-old nulliparous woman presented to our Gynecology Oncology facility with an abdominal mass that had progressively increased in size over the last three months. She had a history of papillary thyroid cancer ten years previously and was treated with radioiodine (I-131). Physical examination revealed an immobile abdominal cystic mass measuring 20 × 18 × 15 cm. Ultrasound imaging revealed a cystic mass with a solid part, measured 16.1 × 10.9 × 12.84 cm, with M4 feature of the IOTA simple rule. CA-125 tumor marker levels were 190.1 U/mL. Ovarian cancer was suspected, and surgical staging with total hysterectomy, bilateral salpingo-oophorectomy, omentectomy, frozen sectioning, and adhesiolysis was performed. Histopathological examination revealed a clear cell ovarian carcinoma.

Discussion

Papillary thyroid carcinoma tends to be a locoregional metastasis, whereas distant metastases are rare. Distant metastasis often occurs decades after the primary tumor, with the most common metastatic sites being the lungs and bones. This raises an important clinical question concerning the etiology of the ovarian carcinoma: whether it represents a metastasis from the pre-existing thyroid carcinoma or a distinct primary neoplasm. Determining the precise relationship between these malignancies is crucial for guiding treatment strategies and understanding the biological behavior of the tumors involved. In this case, clear cell ovarian carcinoma arose separately from papillary thyroid carcinoma.

Conclusion

Double primer cancer of the ovary and thyroid, which is a clear cell ovarian carcinoma metachronous with papillary thyroid carcinoma, is possible.

Principles of Analytic Validation of Immunohistochemical Assays: Guideline Update

CONTEXT.—

In 2014, the College of American Pathologists developed an evidence-based guideline to address analytic validation of immunohistochemical assays. Fourteen recommendations were offered. Per the National Academy of Medicine standards for developing trustworthy guidelines, guidelines should be updated when new evidence suggests modifications.

OBJECTIVE.—

To assess evidence published since the release of the original guideline and develop updated evidence-based recommendations.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and update the original guideline recommendations using the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS.—

Two strong recommendations, 1 conditional recommendation, and 12 good practice statements are offered in this updated guideline. They address analytic validation or verification of predictive and nonpredictive assays, and recommended revalidation procedures following changes in assay conditions.

CONCLUSIONS.—

While many of the original guideline statements remain similar, new recommendations address analytic validation of assays with distinct scoring systems, such as programmed death receptor-1 and analytic verification of US Food and Drug Administration approved/cleared assays; more specific guidance is offered for validating immunohistochemistry performed on cytology specimens.

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

CONTEXT.—

Immunohistochemistry has become a valuable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

OBJECTIVE.—

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

DATA SOURCES.—

Literature review and the author's research data and personal practice experience.

CONCLUSIONS.—

This review article highlights that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoid potential diagnostic errors.

Neoplasms in Struma Ovarii: A Review

Struma ovarii is a well-known ovarian teratoma made up of benign thyroid tissue. These lesions demonstrate variable, normal architecture and normal thyroid immunohistochemical staining with positivity for TTF1, PAX8, and thyroglobulin. Though most are benign, some of these lesions can also present with a malignant component. Within this article, we review the most common diagnostic malignancies including papillary thyroid carcinoma, strumal carcinoid, highly differentiated follicular thyroid carcinoma, and other thyroid carcinomas. We additionally review the use of TTF1 staining to assist in differentiating these lesions from surrounding gynecologic epithelium, which is imperative in making such diagnoses. In highlighting these entities, we hope to provide practicing pathologists with an effective and concise review of these lesions to assist in more challenging cases of struma ovarii.

Thyroid transcription factor-1 expression in rectal adenocarcinoma metastatic to the lung

Distinguishing metastatic lung tumors from primary lung cancer is essential for planning the appropriate treatment strategy. Thyroid transcription factor-1 (TTF-1) is a reliable immunohistochemistry (IHC) marker for differentiating between primary lung adenocarcinomas and metastatic lung tumors originating from colorectal adenocarcinomas. Herein, we report a rare case of TTF-1 expression in both the metastatic lung tumor and primary rectal adenocarcinoma. Aside from the similar histological characteristics of both tumors when stained with hematoxylin-eosin, the IHC patterns, including negative results for alveolar epithelium markers (napsin A and CK7) and positive results for intestinal markers (CK20, CDX2, SATB2, and β-catenin), of the lung tumor and the primary rectal adenocarcinoma strongly supported the final diagnosis. Considering the non-negligible frequency of TTF-1 positivity in colorectal adenocarcinomas, applying the IHC panel including multiple markers for alveolar epithelium and intestinal differentiation, would be helpful to support the diagnosis of metastatic lung tumor from a rectal adenocarcinoma.

The complex and often confusing history, histology and histogenesis of mesonephric, STK11 adnexal tumour and mesonephric-like neoplasms of the upper female genital tract (including broad ligament)

Mesonephric lesions in the female genital tract are uncommon, with those arising from the upper tract being much less frequent than those developing in the lower tract (mesonephric hyperplasia and carcinoma). The most common upper tract lesions include rete cyst/cystadenoma and female adnexal tumour of Wolffian origin (FATWO). The integration of morphological, immunohistochemical and molecular studies on FATWOs has enabled recognition of a novel entity, the STK11 adnexal tumour, which is often associated with Peutz-Jeghers syndrome (~50%) and frequently has a salivary gland morphology but an unknown origin. Similarly, 'mesonephric-like' adenocarcinoma, an entity with striking similarities to mesonephric carcinoma but currently favoured to be of Müllerian derivation based on its association with other Müllerian tumours and molecular findings, has also been recently described, and may histologically mimic both FATWOs and STK11 adnexal tumours. In this review, we provide a historical overview of upper female genital tract mesonephric proliferations and discuss mesonephric lesions, STK11 adnexal tumour, mesonephric-like adenocarcinoma, and mimickers, the most common being endometrioid carcinoma.

Cancer of Unknown Primary: Challenges and Progress in Clinical Management

Distant metastases are the main cause of cancer-related deaths in patients with advanced tumors. A standard diagnostic workup usually contains the identification of the tissue-of-origin of metastatic tumors, although under certain circumstances, it remains elusive. This disease setting is defined as cancer of unknown primary (CUP). Accounting for approximately 3-5% of all cancer diagnoses, CUPs are characterized by an aggressive clinical behavior and represent a real therapeutic challenge. The lack of determination of a tissue of origin precludes CUP patients from specific evidence-based therapeutic options or access to clinical trial, which significantly impacts their life expectancy. In the era of precision medicine, it is essential to characterize CUP molecular features, including the expression profile of non-coding RNAs, to improve our understanding of CUP biology and identify novel therapeutic strategies. This review article sheds light on this enigmatic disease by summarizing the current knowledge on CUPs focusing on recent discoveries and emerging diagnostic strategies.

Practical Application of Lineage-Specific Immunohistochemistry Markers: Transcription Factors (Sometimes) Behaving Badly

CONTEXT.—

Transcription factors (TFs) are proteins that regulate gene expression and control RNA transcription from DNA. Lineage-specific TFs have increasingly been used by pathologists to determine tumor lineage, especially in the setting of metastatic tumors of unknown primary, among other uses. With experience gathered from its daily application and increasing pitfalls reported from immunohistochemical studies, these often-touted highly specific TFs are not as reliable as once thought.

OBJECTIVES.—

To summarize the established roles of many of the commonly used TFs in clinical practice and to discuss known and potential sources for error (eg, false-positivity from cross-reactivity, aberrant, and overlap "lineage-specific" expression) in their application and interpretation.

DATA SOURCES.—

Literature review and the authors' personal practice experience were used. Several examples selected from the University Health Network (Toronto, Ontario, Canada) are illustrated.

CONCLUSIONS.—

The application of TF diagnostic immunohistochemistry has enabled pathologists to better assess the lineage/origin of primary and metastatic tumors. However, the awareness of potential pitfalls is essential to avoid misdiagnosis.

Diagnostic Utility of Thyroid Transcription Factor-1 in Ovarian Carcinoma and Its Relationship With Clinicopathologic Prognostic Parameters

Although thyroid transcription factor-1 (TTF-1) is considered a relatively sensitive and specific marker for lung and thyroid neoplasms, it can occasionally be expressed in other tumors. Few immunohistochemical studies have been conducted on TTF-1 expression in ovarian carcinomas with discrepant results. To date, only 1 study compared different TTF-1 clones in ovarian carcinoma. This study is designed to evaluate the expression of TTF-1 clones in ovarian carcinomas and investigate TTF-1 association with clinicopathologic prognostic parameters. A retrospective immunohistochemical study was conducted on 62 primary ovarian carcinomas and 15 normal ovarian tissues using 2 clones of TTF-1 antibody (SPT24 and 8G7G3/1). Nuclear expression of SPT24 and 8G7G3/1 clones of TTF-1 was detected in 17.7% and 3.2% of ovarian carcinomas, respectively. Positive cytoplasmic immunostaining of clone SPT24 was detected in 1.6% of cases. In contrast, normal ovarian tissue showed negative expression of both clones. A highly significant difference was observed between both clones regarding their sensitivity in ovarian carcinomas (P=0.004). A significant inverse relationship was observed between TTF-1 (SPT24 clone) expression and tumor stage (P=0.022). TTF-1 expression is not exclusive to lung and thyroid tissue. It is expressed in ovarian carcinomas where clone SPT24 is more sensitive than clone 8G7G3/1. TTF-1 might be of diagnostic utility in evaluating neoplasms of unknown primary origin as well as adenocarcinomas involving the lung in patients with a history of a gynecologic malignancy. Moreover, TTF-1 expression might be a good prognostic factor in ovarian carcinoma.

Best Practices Recommendations for Diagnostic Immunohistochemistry in Lung Cancer

Since the 2015 WHO classification was introduced into clinical practice, immunohistochemistry (IHC) has figured prominently in lung cancer diagnosis. In addition to distinction of small cell versus non-small cell carcinoma, patients' treatment of choice is directly linked to histologic subtypes of non-small cell carcinoma, which pertains to IHC results, particularly for poorly differentiated tumors. The use of IHC has improved diagnostic accuracy in the classification of lung carcinoma, but the interpretation of IHC results remains challenging in some instances. Also, pathologists must be aware of many interpretation pitfalls, and the use of IHC should be efficient to spare the tissue for molecular testing. The International Association for the Study of Lung Cancer Pathology Committee received questions on practical application and interpretation of IHC in lung cancer diagnosis. After discussions in several International Association for the Study of Lung Cancer Pathology Committee meetings, the issues and caveats were summarized in terms of 11 key questions covering common and important diagnostic situations in a daily clinical practice with some relevant challenging queries. The questions cover topics such as the best IHC markers for distinguishing NSCLC subtypes, differences in thyroid transcription factor 1 clones, and the utility of IHC in diagnosing uncommon subtypes of lung cancer and distinguishing primary from metastatic tumors. This article provides answers and explanations for the key questions about the use of IHC in diagnosis of lung carcinoma, representing viewpoints of experts in thoracic pathology that should assist the community in the appropriate use of IHC in diagnostic pathology.

Applications of Immunohistochemistry to Endocrine Pathology

The role of immunohistochemistry (IHC) in endocrine pathology is similar to that in other organ systems in that it can aid in the subclassification of tumors within an organ, confirm site of primary in metastatic disease, provide prognostic information, identify underlying genetic alterations, and predict response to treatment. Although most endocrine tumors do not require IHC to render a diagnosis, there are certain scenarios in which IHC can be extremely helpful. For example, in thyroid, IHC can be used to support tumor dedifferentiation, in the adrenal it can aid in the diagnosis of low-grade adrenocortical carcinomas, and in paragangliomas it can help identify tumors arising as part of an inherited tumor syndrome. This review will focus on the applications of IHC in tumors of the thyroid, parathyroids, adrenals, and paraganglia in adults.

Comparison of Three Different TTF-1 Clones in Resected Primary Lung Cancer and Epithelial Pulmonary Metastases

OBJECTIVES

Immunohistochemical staining against thyroid transcription factor 1 (TTF-1) is often used to distinguish lung adenocarcinoma from squamous cell carcinoma and pulmonary metastasis.

METHODS

TTF-1 expression was examined using the antibody clones 8G7G3/1, SPT24, and SP141 on tissue microarrays from 665 cases of resected lung cancers and 428 pulmonary metastases.

RESULTS

Most lung adenocarcinomas, 89%, 93%, and 93%, were positive with TTF-1 clones 8G7G3/1, SPT24, and SP141, respectively. The corresponding figures for lung squamous cell carcinomas were 0%, 6%, and 8%. In total, five (2%), 19 (7%), and 21 (8%) of the pulmonary metastases from colorectal adenocarcinomas were positive with clones 8G7G3/1, SPT24, and SP141, respectively. Other TTF-1-positive pulmonary metastases (n = 8) were thyroid, urothelial, pancreatic, small bowel, and cervix carcinomas.

CONCLUSIONS

TTF-1 expression in lung cancer and pulmonary metastases differs between clones, with 8G7G3/1 being more specific but less sensitive compared with SPT24 and SP141.

Diffusely Metastasized Adenocarcinoma Arising in a Mucinous Carcinoid of the Ovary: A Case Report

Mucinous (goblet cell) carcinoids are a rare type of ovarian carcinoid tumors. Only a limited number of primary mucinous carcinoids of the ovary have been reported in the literature. We describe the case of a 55-year-old woman with a diffusely metastasized adenocarcinoma arising in a primary ovarian mucinous carcinoid. The differential diagnosis with a metastatic goblet cell carcinoid from the appendix or elsewhere can be very challenging. In our case, especially the immunohistochemical profile of the tumor with diffuse positivity for cytokeratin 7 and PAX8, and no expression of cytokeratin 20 and CDX2, directed us toward a primary ovarian origin. Expression of PAX8 in ovarian mucinous carcinoid has never been reported before.

Evaluation of Carcinoma of Unknown Primary on Cytologic Specimens

Carcinoma of unknown primary is defined as metastatic carcinoma without a clinically obvious primary tumor. Determining the tissue of origin in carcinoma of unknown primary is important for site-directed therapy. Immunohistochemistry is the most widely used tool for the work-up of metastases, but molecular profiling assays are also available. This review provides an overview of immunohistochemical stains in the work-up of metastatic carcinoma, with a focus on newer site-specific markers, and discusses the role of gene expression profiling assays for determining tissue of origin. The utility of cytopathology specimens in the evaluation of carcinoma of unknown primary also is highlighted.

Unexpected endometrial metastasis of a primary lung adenocarcinoma

Following diagnosis of primary malignancies, subsequent workup includes evaluation for metastasis. Each malignancy, both location and histologic features, have statistically common and less common metastatic patterns. Metastatic lung adenocarcinoma typically involves lymph nodes, liver, brain, and bone. Very rarely can it involve the reproductive tract. Specifically, in females, multiple reported cases include ovarian metastasis. Even rarer, endometrial metastasis, such as this case report, has been reported. Even with usual staging utility of PET/CT, common things remain common; knowledge of common metastatic patterns can bias overall interpretation. This case is a reminder that despite our tendencies to focus on frequent patterns, even the rarest of metastatic patterns are still possible.

Diagnostic immunohistochemistry in gynaecological neoplasia: a brief survey of the most common scenarios

Immunohistochemistry is a valuable adjunct in routine gynaecological pathology. The molecular revolution has redesigned knowledge of gynaecological cancers and refined histological classification. The direct consequence has been the progressive introduction of new immunostainings for diagnostic and classification purposes. Hence, we review the routine diagnostic use of immunohistochemistry in the field of gynaecological neoplasia. We reviewed the immunomarkers useful in gynaecological pathology according to literature revision, our personal experience and research findings. We discuss the application of immunohistochemistry to reach the most accurate diagnosis in morphologically equivocal cases of gynaecological pathology and present the appropriate panel of immunomarkers in the most common scenarios of gynaecological pathology. This short review provides an updated overview of the essential immunohistochemical markers currently used in the diagnostics of gynaecological malignancies along with their molecular rationale.

Cervical Carcinomas With Neuroendocrine Differentiation: A Report of 28 Cases With Immunohistochemical Analysis and Molecular Genetic Evidence of Common Clonal Origin With Coexisting Squamous and Adenocarcinomas

Cervical neuroendocrine carcinomas are rare, aggressive tumors and their immunohistochemical features and clonal relationship to coexisting tumors are incompletely described. Twenty-eight cases were identified (17 small cell, 9 large cell, and 2 mixed), 10 of which had an invasive squamous or adenocarcinoma component. Staining for synaptophysin, chromogranin A, TTF1, c-kit, CD44, and p16 was performed. Analyses for loss of heterozygosity (LOH) at 5 polymorphic microsatellite markers (D3S1300, D9S171, D11S914, D13S319, and TP53) and X-chromosome inactivation were performed. Of 17 cases with available blocks, 13 (76%) were synaptophysin+, 8 (47%) were chromogranin A+, 8 (47%) were TTF1+, 7 (41%) were c-kit+, and 6 (35%) were CD44+. Strong patchy or strong diffuse p16 staining was seen in all cases. LOH and X-chromosome inactivation analysis were performed for 17 cases, 8 of which had a coexisting squamous or adenocarcinoma component. Five of the 8 (63%) cases with 2 components showed allelic loss in both components. All 5 of these cases demonstrated identical LOH between the neuroendocrine and squamous or adenocarcinoma components. Nonrandom X-chromosome inactivation was seen in the neuroendocrine and other components in 4 of the 8 cases. In all 4 cases the pattern of inactivation was identical between the 2 components. Cervical neuroendocrine carcinomas have features similar to other extrapulmonary neuroendocrine carcinomas, including expression of TTF1, c-kit, and CD44. Consistent staining for p16 is also seen. Concordant genetic alterations support common clonal origin for neuroendocrine carcinomas with a coexisting squamous or adenocarcinoma component.

Thyroid transcription factor-1 promotes lymph node metastasis by inducing lymphangiogenesis in ovarian carcinoma

AIMS AND BACKGROUND

Thyroid transcription factor-1 (TTF-1) expression is widely considered a specific marker for lung and thyroid carcinomas and plays an important role in angiogenesis in lung cancer. However, it can occasionally be expressed in other malignancies, including ovarian carcinomas, and the mechanism of TTF-1 in lymphatic metastasis of ovarian carcinomas is still unclear. This study aimed to define the TTF-1 expression and lymph vessel density (LVD) in ovarian carcinomas and look for their correlations with clinicopathological features.

METHODS

We examined the incidence of thyroid transcription factor 1 expression (clone SPT24) and lymph vessel density (LVD) quantified through D2-40 by immunohistochemistry from 110 primary ovarian carcinomas and 40 benign ovarian tumor as controls in Chinese patients.

RESULTS

Thyroid transcription factor 1 was detected in 28 primary ovarian carcinomas (25.5%), which was significantly higher than its expression in benign ovarian tumor. TTF-1 expression was correlated with tumor FIGO stage,T stage and lymphatic metastasis. Moreover, LVD was associated with tumor FIGO stage, TNM stage. Furthermore, the LVD counts in group of TTF-1 positive expression were higher than in group of TTF-1 negative expression.

CONCLUSIONS

These findings indicated the occasional expression of TTF-1 immunoreactivity of ovarian carcinomas should be considered in the evaluation of neoplasms of unknown primary origin and TTF-1 might be involved in lymph node metastasis of ovarian carcinomas in the presence of lymphangiogenesis.

TTF-1-positive Metastatic Endometrioid Carcinoma: A Case Report and Review of Literature of a Potential Diagnostic Pitfall

A 75-year-old female patient, nonsmoker was addressed to our institution for a fracture of C5 vertebra with spinal cord compression by a tumor mass invading surrounding soft tissue. She had a previous history of breast ductal carcinoma and endometrioid carcinoma. Biopsy of the tumor mass showed a TTF-1-positive carcinoma. Molecular study showed a E545K mutation of PIK3CA. Lung imaging showed multiple nodules evocative of metastasis rather than a primitive tumor. Reviewing of slides of endometrioid carcinoma showed areas positive for TTF1, and the same E545K mutation was found in endometrial tumor. The final diagnosis was endometrioid metastatic carcinoma with aberrant TTF-1 expression. A subset of endometrial neoplasm expresses TTF-1, this situation might be confusing especially in case of metastatic disease.

Roles of Thyroid Transcription Factor 1 in Lung Cancer Biology

Thyroid transcription factor 1 (TTF-1 or NKX2-1) is a transcription factor of fundamental importance in driving lung maturation and morphogenesis. In the last decade, scientists began to appreciate the functional roles of TTF-1 in lung tumorigenesis. This movement was triggered by the discoveries of genetic alterations of TTF-1 in the form of gene amplification in lung cancer. Many downstream target genes of TTF-1 relevant to the lung cancer biology of TTF-1 have been documented. One of the most surprising findings was that TTF-1 may exhibit either pro- or antitumorigenic activities, an outcome with the complexity exceeding the original anticipation purely based on the fact that TTF-1 undergoes gene amplification in lung cancer. In the coming decade, we believe, we will witness additional surprises as the research exploring the cancer roles of TTF-1 progresses.

High-level expression of divergent endodermal lineage markers in gonadal and extra-gonadal yolk sac tumors

Yolk sac tumors occur at both gonadal and extra-gonadal sites. A recent case of ovarian endometrioid-pattern yolk sac tumor with strong diffuse expression of TTF-1 illustrated the potential for misdiagnosis due to divergent expression of endodermal lineage markers. The aim of this study was to investigate the expression of four divergent endodermal lineage markers, TTF-1, CDX2, Hep Par 1, and Napsin A, in gonadal and extra-gonadal yolk sac tumors of differing age, sex, and location (excluding foci of overt hepatoid differentiation). We identified 26 cases (5 ovarian, 15 testicular, and 6 extra-gonadal) containing yolk sac tumor as identified by typical histology and confirmed by positive immunohistochemical staining for alpha-fetoprotein and glypican-3. Mixed or ambiguous foci were confirmed by immunohistochemistry (SALL4 positive and Oct-4 negative). The relative proportion of three histologic patterns: reticular/cystic, solid/myxoid, and glandular was estimated. Percent positivity for the four divergent endodermal lineage markers was compared within yolk sac tumor areas according to site, age group, and histologic pattern. High-level (>25%) staining for one or more divergent endodermal lineage markers was seen in eleven cases: Hep Par 1 in seven cases, all post-pubertal, TTF-1 in four cases, two ovarian and two extra-gonadal, and CDX2 in three cases, with no age or site predilection. No case highly expressed all three divergent endodermal lineage markers, but four co-expressed high levels of two markers: two ovarian yolk sac tumors with TTF-1 and Hep Par 1, one testicular yolk sac tumor with CDX2 and Hep Par 1, and one extra-gonadal yolk sac tumors with TTF-1 and CDX2. While no absolute correlation of high-level divergent endodermal lineage marker expression with histologic subtype was observed, TTF-1 and CDX2 expression was predominantly seen in reticular/cystic and glandular areas while Hep Par 1 was most frequent in myxoid/solid and glandular areas.

Hormone receptor-negative, thyroid transcription factor 1-positive uterine and ovarian adenocarcinomas: report of a series of mesonephric-like adenocarcinomas

AIMS

To report a series of uterine corpus (n = 7) and ovarian (n = 5) neoplasms which we believe probably represent mesonephric adenocarcinomas based on their characteristic morphology and immunophenotype.

METHODS AND RESULTS

All neoplasms exhibited a relatively constant and characteristic morphological appearance with an admixture of architectural patterns with small glands or tubules, some containing luminal eosinophilic colloid-like material, typically predominating. Solid and papillary architectures were also often present. The nuclear features were characteristic with atypical angulated clear vesicular nuclei which often exhibited overlapping. All the tumours were 'flat' negative with oestrogen receptor and progesterone receptor and all except one exhibited nuclear staining with thyroid transcription factor 1 (TTF1), which was often diffuse. All tumours exhibited wild-type staining with p53. CD10, calretinin and GATA binding protein 3 (GATA3) were positive in a variable proportion of the neoplasms.

CONCLUSIONS

We believe these neoplasms to represent mesonephric adenocarcinomas which have only rarely been reported to arise in the uterine corpus and never in the ovary. We recommend they be termed mesonephric-like adenocarcinomas until their histogenesis is firmly established.

Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site

CONTEXT

-Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes.

OBJECTIVES

-To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features.

DATA SOURCES

-Literature review, the authors' practice experience, and authors' research.

CONCLUSIONS

-With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls.

Endometrial metastasis of lung adenocarcinoma: a report of two cases

Case series

Patient: Female, 55 • Female, 51

Final Diagnosis: Metastatic lung adenocarcinoma

Symptoms: Neck swelling

Medication: Erlotinib

Clinical Procedure: Lymph node biopsy

Specialty: Oncology

Immunohistochemistry in undifferentiated neoplasm/tumor of uncertain origin

CONTEXT

Immunohistochemistry has become an indispensable ancillary study in the identification and classification of undifferentiated neoplasms/tumors of uncertain origin. The diagnostic accuracy has significantly improved because of the continuous discoveries of tissue-specific biomarkers and the development of effective immunohistochemical panels.

OBJECTIVES

To identify and classify undifferentiated neoplasms/tumors of uncertain origin by immunohistochemistry.

DATA SOURCES

Literature review and authors' research data and personal practice experience were used.

CONCLUSIONS

To better guide therapeutic decisions and predict prognostic outcomes, it is crucial to differentiate the specific lineage of an undifferentiated neoplasm. Application of appropriate immunohistochemical panels enables the accurate classification of most undifferentiated neoplasms. Knowing the utilities and pitfalls of each tissue-specific biomarker is essential for avoiding potential diagnostic errors because an absolutely tissue-specific biomarker is exceptionally rare. We review frequently used tissue-specific biomarkers, provide effective panels, and recommend diagnostic algorithms as a standard approach to undifferentiated neoplasms.

Application of Immunohistochemistry in Thyroid Pathology

Context

Accurate classification of follicular-patterned thyroid lesions is not always an easy task on routine surgical hematoxylin-eosin–stained or cytologic fine-needle aspiration specimens. The diagnostic challenges are partially due to differential diagnostic criteria that are often subtle and subjective. In the past decades, tremendous advances have been made in molecular gene profiling of tumors and diagnostic immunohistochemistry, aiding in diagnostic accuracy and proper patient management.

Objective

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of thyroid pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine) from 1976–2013.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method may complement the morphologic assessment and aid in the accurate classification of difficult thyroid lesions.

The lung-restricted marker napsin A is highly expressed in clear cell carcinomas of the ovary

OBJECTIVES

We recently observed expression of the "lung" marker napsin A in ovarian clear cell carcinomas and therefore sought to determine the extent of napsin A expression in a subset of ovarian neoplasms.

METHODS

We identified an archival series of ovarian clear cell carcinomas (n = 36), serous borderline tumors (n = 21), high-grade serous carcinomas (n = 37), and endometrioid adenocarcinomas (n = 29). Using standard immunohistochemical techniques on whole sections of formalin-fixed, paraffin-embedded specimens, we employed a panel of antibodies: napsin A (IP64), estrogen receptor (SP1), WT-1 (6F-H2), PAX-8 (BC12), and TTF-1 (SPT24).

RESULTS

Thirty-six of 36 clear cell carcinomas showed napsin A expression, typically in a uniform pattern. None of the serous borderline tumors or high-grade serous carcinomas manifested napsin A expression. Napsin A was expressed in three (10%) of 29 endometrioid adenocarcinomas, generally in a focal pattern.

CONCLUSIONS

Our study showed that napsin A is an extremely sensitive (100%) marker of ovarian clear cell carcinomas and exhibits very high specificity (100%) in distinguishing clear cell carcinomas from high-grade serous carcinomas and serous borderline tumors and 90% specificity in discriminating clear cell carcinomas from endometrioid carcinomas.

Principles of analytic validation of immunohistochemical assays: Guideline from the College of American Pathologists Pathology and Laboratory Quality Center

CONTEXT

Laboratories must validate all assays before they can be used to test patient specimens, but currently there are no evidence-based guidelines regarding validation of immunohistochemical assays.

OBJECTIVE

To develop recommendations for initial analytic validation and revalidation of immunohistochemical assays.

DESIGN

The College of American Pathologists Pathology and Laboratory Quality Center convened a panel of pathologists and histotechnologists with expertise in immunohistochemistry to develop validation recommendations. A systematic evidence review was conducted to address key questions. Electronic searches identified 1463 publications, of which 126 met inclusion criteria and were extracted. Individual publications were graded for quality, and the key question findings for strength of evidence. Recommendations were derived from strength of evidence, open comment feedback, and expert panel consensus.

RESULTS

Fourteen guideline statements were established to help pathology laboratories comply with validation and revalidation requirements for immunohistochemical assays.

CONCLUSIONS

Laboratories must document successful analytic validation of all immunohistochemical tests before applying to patient specimens. The parameters for cases included in validation sets, including number, expression levels, fixative and processing methods, should take into account intended use and should be sufficient to ensure that the test accurately measures the analyte of interest in specimens tested in that laboratory. Recommendations are also provided for confirming assay performance when there are changes in test methods, reagents, or equipment.

Müllerian-type, cutaneous ciliated cyst in the gluteal cleft mimicking a pilonidal cyst

A cutaneous ciliated cyst is a rare entity found predominantly in the lower extremities and perineal region of young females. Although initially described by Hess in 1890, the present day term, "cutaneous ciliated cyst," was proposed by Farmer in 1978 and includes a wide array of cyst types. Despite their typical female predominance and location, many have described cutaneous ciliated cysts in males and atypical locations. In addition, Mullerian cysts in the posterior mediastinum and the retroperitoneum have been reported. To date, only 40 cases have been reported in the literature of a Mullerian-type, cutaneous ciliated cyst. Here, we report a case of 13-year-old female with one in the gluteal cleft, initially presenting as a pilonidal cyst. We also discuss the differential diagnosis of pediatric sacrococcygeal lesions and pathogenesis of a Mullerian-type, cutaneous ciliated cyst.

Warranting investigation of primary lung adenocarcinoma in patients with an extrapulmonary malignancy and lung nodules due to high frequency

OBJECTIVES

To distinguish primary lung adenocarcinoma (PLA) from metastatic adenocarcinoma/malignancy to optimize therapy.

METHODS

We investigated the utility of thyroid transcription factor 1 (TTF-1) and napsin A in distinguishing PLA from metastatic adenocarcinoma/malignancy and assessed the frequency of PLA in patients with extrapulmonary malignancy/adenocarcinoma (PLA-EPM/EPA).

RESULTS

TTF-1 and napsin A identified PLA in PLA-EPM/ EPA with a sensitivity of 89.4% and 93.3% and a specificity of 93.9% and 94.7%, respectively. PLA was confirmedin 47.4% of PLA-EPM and 40.2% of PLA-EPA. Overall, 38.5% of patients with PLA had EPM. The common organs for PLA-EPA were breast (35.8%), colon (13.2%), and others, whereas the common organs resulting in pulmonary metastasis were the colon (32.8%), breast (28.1%), and others. A patient with a smoking history and without EPM had a higher chance of having PLA. Multiple nodules are not a reliable indication of metastatic adenocarcinoma.

CONCLUSIONS

Our results firmly support the role of TTF-1 and napsin A in identifying PLA-EPM/EPA. We reason that all new lung nodules in patients with a history of EPM should be screened using these techniques due to the high frequency of PLA-EPM, which will affect treatment and prognosis of patients with EPM/EPA.

Immunohistochemistry in the differential diagnostics of primary lung cancer: an investigation within the Southern Swedish Lung Cancer Study

OBJECTIVES

To assess immunohistochemical (IHC) stains differentially expressed between different types of lung cancer.

METHODS

We evaluated 16 different IHC stains in 209 prospectively included, surgically treated primary lung cancers, including 121 adenocarcinomas, 65 squamous cell carcinomas, 15 large-cell carcinomas, 5 adenosquamous carcinomas, 2 sarcomatoid carcinomas, and 1 small-cell carcinoma, using the tissue microarray technique.

RESULTS

Cytokeratin 5 (CK5) and P63 were both positive in 10% or more of the cells in 97% of the squamous cell carcinomas, with the former being positive (<10% of the cells) in only 2 non-squamous cell carcinomas. Thyroid transcription factor 1 (TTF1) and napsin A were positive in 10% or more of the cells in 88% and 87% of the adenocarcinomas, respectively, with 94% of the adenocarcinomas being positive in at least 1 marker. Fifteen percent of the adenocarcinomas were positive for estrogen receptor.

CONCLUSIONS

CK5, TTF1, and napsin A are sensitive markers for squamous cell carcinoma and adenocarcinoma of the lung.

Value of thyroid transcription factor-1 immunostaining in tumor diagnosis: a review and update

Thyroid transcription factor-1 (TTF-1) is a tissue-specific transcription factor that plays a critical role in the normal development of embryonic epithelial cells of the thyroid and lung. Because TTF-1 expression is highly restricted to epithelial tumors arising in these organs, it is, at present, one of the immunohistochemical markers most commonly used to assist in the differential diagnosis of carcinomas of the lung and thyroid. Recent studies, however, have reported that TTF-1 is not as specific for lung and thyroid carcinomas as was previously thought as it can be found to be expressed, although much less frequently, in some carcinomas arising in other organs, such as the ovaries, endometrium, colon, and breast, as well as in some tumors of the central nervous system. Even though this unexpected TTF-1 positivity has been reported more frequently with the recently available SPT24 anti-TTF-1 monoclonal antibody, it has also been shown to occur with the commonly used 8G7G3/1 clone, albeit in a lower percentage of cases. Despite these findings, TTF-1 remains a very useful immunohistochemical marker in diagnostic pathology.

Comparison of monoclonal napsin A, polyclonal napsin A, and TTF-1 for determining lung origin in metastatic adenocarcinomas

Thyroid transcription factor 1 (TTF-1) is currently the best immunohistochemical marker for carcinomas of lung origin. Our aim was to compare napsin A to TTF-1 for identifying pulmonary origin in metastatic adenocarcinoma and its mimics. One hundred fifty-five metastatic carcinomas (55 pulmonary, 100 nonpulmonary) were stained with monoclonal napsin A and TTF-1, and most also with polyclonal napsin A. The sensitivity of monoclonal napsin A, polyclonal napsin A, and TTF-1 for metastatic adenocarcinomas of pulmonary origin was 76%, 81%, and 82%, respectively. Two lung carcinomas were diffusely positive for monoclonal napsin A, but negative or equivocal for TTF-1. TTF-1 stained 9 of 100 nonpulmonary carcinomas (all thyroid), monoclonal napsin A stained 12 of 100 (4 sites), and polyclonal napsin A stained 27 of 91 (8 sites). Napsin A is expressed in a wider variety of metastatic nonpulmonary carcinomas than TTF-1, and the monoclonal antibody is more specific. Napsin A is a useful adjunct to TTF-1, because occasional lung adenocarcinomas are TTF-1 negative but napsin A positive.

Expression of thyroid transcription factor-1 in normal endometrium is associated with risk of endometrial cancer development

Thyroid transcription factor-1 (TTF-1) is a DNA-binding protein that is mainly expressed in thyroid and lung tissue, but has also been found in gynecologic tissue. Recent studies have suggested that TTF-1 has tumor suppressor function in lung adenocarcinoma models. In the current study, we examined whether expression of TTF-1 in benign endometrium and endometrial hyperplasia might impact on the risk of developing endometrial cancer. Formalin-fixed paraffin-embedded endometrial tissues obtained from 535 cases were used to construct an endometrial tissue microarray. One hundred fifty of 207 patients had multiple serial endometrial specimens including 46 patients who progressed to endometrial cancer. The tissue microarray included a range of histopathologies including benign endometrium (n=231), simple hyperplasia (n=105), complex hyperplasia (n=36), simple atypical hyperplasia (n=10), complex atypical hyperplasia (n=44), and endometrial carcinoma (n=109). Expression of TTF-1 by immunohistochemistry in benign endometrium and endometrial hyperplasia was correlated with progression to cancer and clinical features known to be associated with increased risk of developing endometrial cancer. Carcinoma specimens showed a significantly greater expression of TTF-1 compared with benign endometrium and non-atypical hyperplasia (P=0.0007 and P=0.05). Presence of TTF-1 expression in benign endometrium was associated with a significantly decreased risk of cancer development (P=0.003, hazards ratio=0.104, 95% CI: 0.024-0.455). TTF-1 expression in hyperplasia did not significantly correlate with progression to cancer. The data from our study show that TTF-1 expression in normal endometrium is associated with a reduced risk of endometrial cancer development. This observation suggests that TTF-1 might function as a tumor suppressor in endometrial tissue. TTF-1 expression in normal endometrium could potentially provide clinically useful information as a biomarker for the risk of endometrial cancer.