Choriocarcinoma-like lesions in patients with testicular germ cell tumors. Two histologic variants.

Nine men with testicular germ cell tumors developed one of two types of histologically similar cystic lesions that had features of choriocarcinoma. In five cases, these choriocarcinoma-like lesions (CCLL) were felt to represent an unusual proliferation of teratomatous epithelium (teratomatous CCLL); whereas in four cases, the CCLL was felt to represent a nonbiphasic and cystic form of choriocarcinoma similar to the atypical choriocarcinoma described by Mazur et al. except for its cystic nature. Both types usually occurred as focal findings associated with teratomas. Eight of nine patients had received chemotherapy prior to excision of the CCLL. Teratomatous CCLLs often had a lacelike arrangement of atypical epithelium around cysts that contained homogeneous secretion. Mucicarmine stains were positive in four of five cases of teratomatous CCLLs. Cystic atypical choriocarcinoma consisted of stratified mononucleated cells lining cysts containing a coagulum of eosinophilic material. Stains for human chorionic gonadotropin (HCG) were positive in three of four cases of cystic atypical choriocarcinoma, although serum HCG elevations were either negative or just slightly elevated preoperatively. Five patients with a CCLL who were clinically free of disease following surgical excision and who received no additional chemotherapy remained well on follow-up (average, 1.9 years). We encourage the separate recognition of these lesions so that future studies may determine their clinical significance more precisely.