The central nervous system (CNS) germ cell tumors are a rare and heterogeneous group of tumors, that are highly responsive to chemotherapy. The family of tumors known as germ cell tumors can develop anywhere in the body, most commonly in the male testicles and female ovaries, but also in other locations in the pelvis, abdomen, chest and brain. These tumors are considered to arise from nests of embryonic cells that were traveling along the primitive notochord during early fetal development down to their usual locations (ie. to the genitals), but somehow became arrested in their migration.
Those tumors arising in the brain do so mainly from mid-line locations of the pineal gland (at the rear end of the third ventricle) and the suprasellar and hypothalamic region (at the front end of the third ventricle).
What causes these primitive embryonic cells to undergo transformation into cancers is not known. These tumors are found only very rarely in more than one family member, so a genetic association is not the usual reason. Of interest, however, is that these tumors are far more common in South-East Asian countries than in North or South America or in Europe. No environmental factors have been linked to the development of these tumors, except that the drug diethylstilbestrol (DES) used several decades ago to stabilize unstable pregnancies, and known to be associated with the development of vaginal cancer in offspring of woman taking the drug during pregnancy, has also been less convincingly linked to testicular cancer in offspring. Testicular cancer (but not other forms of germ cell cancers) has been clearly associated with the failure of testicles to descend from the abdomen into the scrotal sac of young boys.