In Japan, germ cell tumors constitute 2% to 9% of all intracranial tumors, with a male preponderance. The incidence is less in the west and other countries. Germ cell tumors are thought to arise from primitive cell nests found along the embryonic midline.

They include, germinoma, mature, immature, and malignant teratoma, choriocarcinoma, endodermal sinus tumor, embryonal cell carcinoma, and tumors of combined histology.

Two thirds of all are germinomas. Teratomas are the next commonest.

Teratomas and choriocarcinomas occur more commonly in childhood. Most other tumors are diagnosed during second decade of life, raising the possibility of an associated neuroendocrine changes taking place during puberty.

Overall, germ cell tumors of the CNS most commonly arise in the pineal and suprasellar regions, pineal site being more common in boys than in girls. Germinomas occur equally in suprasellar and pineal regions. Germ cell tumors account for more than half of all pineal region tumors. Others germ cells tumors are more commonly found in the suprasellar region. Other sites include, sacrococcygeum, retroperitoneum, nasopharynx. They are much less frequent. There are occasional reports of involvement of chiasma, thalamus, cerebellum, and septum pellucidum.

Germ cell tumors have a propensity to disseminate, either via CSF pathways or by infiltration of contiguous structures in the range of 10% to 22%. The rate is high (40%) in choriocarcinomas, and endodermal sinus tumors.

Pure germinomas account for 65% to 72% of all intracranial germ cell tumors. Germinomas are poorly circumscribed and often seed the ventricular system. They may infiltrate the surroundings. The germinoma usually presents dark lobulated surface and grows to a large size, so that its precise site of origin, often remains unclear.

The relationship between embryonal carcinoma, teratocarcinoma, endodermal sinus tumor and yolk sac tumor, though close, is ill-defined.

Embryonal carcinoma is the most primitive of these tumors, and the least frequently reported intracranial germ cell tumor. It is a primitive neoplasm composed of pluripotential epithelial cells.  This tumor rarely found in its pure form, is usually highly malignant and is composed of sheets of cuboidal to columnar cells with large vesicular nuclei and distinct nucleoli.

Endodermal sinus tumors are rare and usually highly invasive, and characterized by a reticular network of cuboidal epithelium, occasionally arranged in papillary patterns.  Schiller-Duval bodies characterized by delicate blood vessels surrounded by primitive columnar cells lying in a space lined by flattened cells, are seen.  Globular intra and extracellular eosinophilic masses positive for alpha-fetoprotein are also seen.

Chorion carcinoma occurring in isolation in the pineal-diencephalic region is exceptional.  Areas of syncytiotrophoblastic differentiation are found more commonly in embryonal carcinomas, endodermal sinus tumors and germinomas than in chorion carcinomas. The tumor is characterized by large round cytotrophoblastic cells with clear cytoplasm alongside sheets of multinucleated syncytiotrophoblast cells, associated with prominent blood-filled sinuses.

Grossly, they are granular, reddish brown mass, almost always with hemorrhage and necrosis. As all other tumors of germ-cell origin, choriocarcinoma is usually accompanied by elements of other tumors of this group.

Teratoma are either immature or mature, the former resembling embryonic or fetal tissues and the latter resembling mature or adult tissue. By definition, the term teratoma can be used only in cases where tumor elements derive from two or three germ layers.  These tumors are usually well-circumscribed, round or lobulated, and multicystic, and compress the surrounding structures. The cystic component may be watery, mucoid or sebaceous.  Sometimes bone, cartilage, hair or teeth is present.  Immature tumours are more frequently associated with a malignant course.

Microscopically, combinations of tissue elements from the various germ cell layers are seen in varying proportions.

positive for ‘cytokeratin’ and for ‘epithelial membrane antigen’.

PLAP (placental Alkaline Phosphatase), beta-hCG (SCT cells) are specific for germinomas.

AFP is positive in glandular components of teratomas. 

Pineal cell tumor markers include melatonin and the S antigen.

Currently, the recommended treatment include, surgery, followed by appropriate chemo and radiotherapy.

A preoperative staging with neuroaxis imaging and CSF analysis, when possible is recommended.

Germinomas, are highly radiosensitive and carry the best prognosis, with 5 year survival rates in the range of 85%, and 10 years rate of 65%.

It has been suggested that teratomas, excised completely, do not require any further treatment.

Survival for other germ cell tumors is much less optimistic.