Immunohistochemistry of germ cell and trophoblastic neoplasms

The immunoprofiles of 121 germ cell and trophoblastic neoplasms were defined, using a battery of antibodies against cytokeratin (CK), vimentin (VIM), epithelial membrane antigen (EMA), placental alkaline phosphatase (PLAP), S-100 protein, leukocyte common antigen (LCA), UCHL-1, LN-2, carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), chromogranin A, Leu-7, alpha-fetoprotein (AFP), alpha-1-antitrypsin (AAT), and the beta subunit of human chorionic gonadotropin (BHCG). In addition to 85 neoplasms of testicular origin, the cases included eight ovarian germ cell tumors and 28 extragonadal neoplasms. All tissues had been subjected to formalin fixation and paraffin embedding. Similar immunoreactivity patterns were seen in gonadal and extragonadal neoplasms, gestational and nongestational choriocarcinomas, components of mixed germ cell tumors and their pure counterparts, and metastatic and primary lesions. Placental alkaline phosphatase was a sensitive marker of germ cell differentiation, and expression of this marker in the absence of EMA appeared to be a staining pattern unique to germ cell tumors. Both LCA and S100 were absent in neoplastic germ cells, and thus were useful in differentiating these tumors from malignant lymphoma and malignant melanoma, respectively. Cytokeratin was helpful in distinguishing seminomas/dysgerminomas from nonseminomatous germ cell tumors, although 10% of seminomas showed focal or diffuse cytokeratin reactivity. Finally, 75% of all germ cell neoplasms displayed NSE, calling the specificity of this determinant into question.