Positive TTF-1 Expression in Malignant Mesothelioma: A Case Report

The role of thyroid transcription factor-1 in differentiating lung adenocarcinomas from non-pulmonary adenocarcinoma effusions

Effusions, characterized by abnormal fluid accumulations in body cavities, present difficulties in identifying the primary organs of metastatic tumors through cytopathologic investigation, particularly in cancer-related complications. This retrospective cross-sectional laboratory study aimed to investigate the role of thyroid transcription factor-1 (TTF-1) in distinguishing lung adenocarcinomas from non-pulmonary adenocarcinomas in effusions. The study was conducted at Almobarak Cytopathology Laboratory, a private cytopathology laboratory. H&E was used to confirm the histological diagnosis of 58 archived cell blocks. TTF-1 immunostaining patterns were then correlated with the histological diagnosis. Statistical analysis, including numerical and graphical data summaries, was conducted using the Chi-square test in SPSS 23. TTF-1 expression was observed in 20 (34.4%) cases, while 38 (65.5%) cases showed no TTF-1 reaction. Positive TTF-1 was found in pleural fluid in 61.1 % of lung adenocarcinomas, while negative TTF-1 was found in only 3.4%. TTF-1 was not detected in the majority of peritoneal fluid samples. There was a highly significant relationship between pleural fluid, TTF-1, and lung adenocarcinoma (p=0.000). The data provided further evidence that TTF-1 is a useful marker for distinguishing pulmonary adenocarcinomas from non-pulmonary adenocarcinoma tumors.

When the Diagnosis of Mesothelioma Challenges Textbooks and Guidelines

The diagnosis of malignant mesothelioma (MPM) does not pose difficulties when presenting with usual clinico-radiologic features and morphology. Pathology textbooks and national/international guidelines generally describe the findings of classic MPM, underlining common clinical presentation, the gold standard of sampling techniques, usual morphologic variants, immunohistochemical results of several positive and negative primary antibodies in the differential diagnosis, and the role of novel molecular markers. Nevertheless, MPM often does not follow the golden rules in routine practice, while the literature generally does not sufficiently emphasize unusual features of its manifestation. This gap may potentially create problems for patients in sustaining a difficult diagnosis of MPM in clinical practice and during legal disputes. Indeed, the guidelines accidentally tend to favor the job of lawyers and pathologists defending asbestos-producing industries against patients suffering from MPM characterized by uncommon features. The current review is aimed at underlining the wide spectrum of clinical and radiological presentation of MPM, the possibility to consistently use cytology for diagnostic intent, the aberrant immunohistochemical expression using so-called specific negative and positive primary antibodies, and finally proposing some alternative and more unbiased approaches to the diagnosis of MPM.

Monoclonal Caveolin 1 Expression in the Differential Diagnosis of Malignant Pleural Mesothelioma and Pulmonary Adenocarcinoma: Is it Useful?

In this study we aim to demonstrate the value of monoclonal Caveolin 1 expression in distinguishing between malignant pleural mesothelioma and pulmonary adenocarcinoma. Total of 129 cases, consisting of 68 cases of malignant pleural mesothelioma (51 epitheloid, 12 biphasic, and 5 sarcomatoid type) and 61 cases of pulmonary adenocarcinoma were examined and stained with monoclonal Caveolin-1. Caveolin 1 expression with a membranous and /or cytoplasmic pattern was detected only in 32.35% (n:22/68) of malignant pleural mesothelioma and 6.5% (n:4/61) of pulmonary adenocarcinoma cases. This finding suggests that the choice of poly/monoclonal antibody for Caveolin 1 in the differential diagnosis of malignant pleural mesothelioma and pulmonary adenocarcinoma is important.

Malignant mesothelioma: A histomorphological and immunohistochemical study of 24 cases from a tertiary care hospital in Southern India

BACKGROUND

Malignant mesotheliomas are histologically heterogeneous neoplasms. Definite diagnosis requires a varied panel of immunohistochemical (IHC) markers to differentiate these from histological mimics. Only a few case series have been reported in the Indian literature where mesotheliomas have been analyzed on routine histology and IHC.

AIM

To evaluate the histological features of malignant mesothelioma and to elucidate the best possible immunomarker combination useful in different scenarios.

MATERIALS AND METHODS

A total of 24 cases of malignant mesotheliomas of different sites encountered over a 6-year period were retrospectively analyzed with regard to their histomorphology and IHC findings.

RESULTS

The pleura was the most common site of involvement (16 cases) followed by peritoneum (5 cases) and pericardium (3 cases). Epithelioid mesothelioma was the most common histological type (15 cases, 62.5%) followed by sarcomatoid (5 cases, 20.84%), deciduoid (2 cases, 8.34%), and 1 case each of desmoplastic and biphasic mesothelioma. Among the mesothelial markers, WT1 was positive in 17 of 20 (85%) cases and calretinin was positive in 20 of 21 (95.23%) cases. D2-40 and CK5/6 were positive in all cases where they were studied. Adenocarcinoma markers TTF-1, napsin A, and CEA had very high negative predictive value in ruling out mesothelioma.

CONCLUSION

The differential diagnosis of mesotheliomas varies with histological type and tumor location. Judicious use of various combinations of IHC markers in different situation has been highlighted in this article.