OVEREXPRESSION OF THE P53 ONCOPROTEIN IN CARCINOMA IN-SITU OF THE TESTIS

Carcinoma in situ (CIS) is regarded as the precursor lesion of testicu lar germ cell tumors. In adults CIS cells have also been described wit hin the normal testicular tissue adjacent to mature teratomas with a f requency of 52-88%. These CIS - cells can be identified by immunohisto chemical staining for ''placental like alkaline phosphastase'' (PLAP). In four of eight patients with mature teratomas CIS was identified by immunohistochemistry for ''PLAP'' in atrophic testicular tubules adja cent to the turners. In three of these patients cells of CIS were posi tive for the p53 oncoprotein, indicating a mutational inactivation of the p53 tumor suppressor gene. The malignant potential of mature terat omas, which do occur without histological signs of malignancy, may the refore be associated with the occurrence of CIS within the histologica lly normal appearing testicular tissue adjacent to the mature tumor. I mmunohistochemical positivity for the p53 protein in CIS cells of some patients may indicate that the mutational inactivation of the p53 tum or suppressor gene could be involved early in the development of testi cular germ cell tumors.