On biopsy, characteristic finding of malignant mesothelioma is - (PGI, June-2010)
a. Most malignant mesothelioma (50% to 60%) are of the epithelial type, approximately 10% are sarcomatoid and the rest are biphasic malignant mesotheliomas.
b. The diagnosis of malignant mesothelioma should be confirmed by immunohistochemistry, which shows that the tumor cells are diffusely positive for pankeratin, keratin 5/6, calretinin and WTl, and negative for the epithelial markers CEA, CD15, Ber-EP4, Moc-31, TTF-1, B72.3 and so forth.
c. For epithelial mesotheliomas, positive staining for pankeratin and calretinin and negative staining for three epithelial markers are considered sufficient for diagnosis.