Diagnostic distinction between unusual malignant tumors of gall bladder by histochemistry and antigenic phenotype.

In a review of 79 cases of gall bladder malignancy, nineteen cases were labelled as unusual tumors while sixty were diagnosed as adenocarcinoma. Alcian blue, PAS, Grimelius' and Masson trichrome stains were done. Expression of EMA, CEA and desmin was assessed (PAP). Histological subtype was revised, in eleven cases out of 19. Five tumors initially diagnosed as squamous cell carcinoma were found to be positive for mucin and CEA and hence were reclassified as adenosquamous carcinoma. Three undifferentiated carcinomas and two malignant carcinoids were labelled as adenocarcinoma and composite tumor respectively. Positive reactivity with CEA and alcian blue PAS and absence of AFP helped in differentiating one giant cell carcinoma from hepatocellular carcinoma. No definite marker could be identified in one case of malignant mesenchymal tumor. Histochemistry and immunohistochemistry also helped in confirming the diagnosis of three cases of carcinoma in situ, one of malignant carcinoid and three of clear cell carcinoma.