Differentiation patterns of testicular germ-cell tumours as revealed by a panel of monoclonal antibodies.

A panel of monoclonal antibodies against different keratin polypeptides, epithelial glycoproteins, placental alkaline phosphatase and collagen type IV was used to evaluate immunohistochemically the expression of the target antigens in 30 different human testicular germ-cell tumours of various types. Antikeratin antibodies detecting markers of different routes of epithelial differentiation revealed remarkable similarity of differential expression of various keratins in epithelial structures of teratomas and combined tumours as compared with normal human epithelial tissues. A considerable proportion of embryonal carcinoma cells stained positively for keratins 8, 18 and 19, while a minor subpopulation of tumour cells in embryonal carcinomas, some seminomas and many atypical intratubular cells expressed keratins 8 and 18 but usually lacked keratin 19. Antibody RICEO-MFG-06.3, specific for epithelial glycoproteins, gave negative results with seminomas as opposed to positivity in all but two nonseminomatous tumours. All but two neoplasms showed positivity for placental alkaline phosphatase, thus supporting its reliability as a marker of germ-cell tumours. It is concluded that the monoclonal antibody RICEO-MFG-06.3 and especially the keratin-19-specific antibodies BA16 and BA17 can be helpful in distinguishing embryonal carcinoma from seminoma and, together with antibodies to other keratins, in the study of the origin and histogenesis of testicular germ-cell tumours.