Differential diagnosis between mesotheliomas and metastatic adenocarcinomas using monoclonal antibodies against gastrointestinal carcinoma antigen and stage-specific embryonic antigen.

Monoclonal antibodies made against gastrointestinal carcinoma antigen (GICA) and stage specific embryonic antigen (SSEA) were evaluated for their ability to distinguish normal mesothelial cells present in pleural and peritoneal fluids from adenocarcinoma cells in tissue and cytology specimens. The presence of GICA was documented in a high percentage of adenocarcinomas from the gastrointestinal tract (75/98) and in 52% of pulmonary (15/29) and 29% of ovarian (6/21) adenocarcinomas. GICA was found infrequently in breast carcinoma (1/18) and not in mesotheliomas (0/16). A similar pattern of GICA expression was seen in malignant effusions from adenocarcinomas (18/47) and mesotheliomas (0/6). SSEA was found in a high percentage of adenocarcinomas derived from the gastrointestinal tract (47/56) and the lung (26/29). SSEA was detected in breast carcinoma (8/15) more often than GICA. SSEA was detected rarely in mesotheliomas (1/16). Reactivities for epithelial membrane antigen, keratin, carcinoembryonic antigen, GICA and SSEA in adenocarcinoma and mesotheliomas were compared.