Pathobiology of intracranial germ-cell tumors: immunochemical, immunohistochemical, and electron microscopic investigations.

In an attempt to clarify the pathobiology of intracranial germ-cell tumors, we studied 56 patients with these tumors, both clinically and pathologically. Our evaluations included immunochemical, immunohistochemical, and electron microscopic observations. Thirty tumors originated in the pineal region, ten in the suprasellar region, nine in the basal ganglia, and two in other regions. Five had double sites of origin. Histologically, there were 39 germinomas, six teratomas, four embryonal carcinomas, two choriocarcinomas and five mixed tumors. Among tumors tested immunochemically, serum carcinoembryonic antigen (CEA) was positive in 3.4%, serum alpha-fetoprotein (AFP) in 25.8%, and serum human chorionic gonadotropin (HCG) in 32.1%. In CSF, CEA was positive in 14.3%, AFP in 26.3%, and HCG in 75%. One third of germinomas were positive for serum HCG, and 88.9% for CSF HCG. One half of teratomas were positive for CEA of CSF. In immunohistochemical testing, the positive rates for CEA, AFP, HCG, and placental alkaline phosphatase (PLAP) were 26.9%, 11.5%, 24.1%, and 55.6%, respectively. Most teratomas were positive for CEA and the reactions were prominent in gland-like structures. HCG-positive syncytial cells were found in three germinomas and two embryonal carcinomas as well as in choriocarcinomas. The majority of germinomas were positive for PLAP and the reactive sites were tumor cell membranes and cytoplasm. On electron microscopy, germinomas were least differentiated, followed in order by embryonal carcinomas, choriocarcinomas, and teratomas. Further clinical and pathological studies will be necessary for a better understanding of the biology of these tumors.