germinomas

Germinomas are a malignant germ cell tumor that most often arises in midline locations of the central nervous system or in gonads, but can occur anywhere germ cells migrate during development. They are the most common type of intracranial germ cell tumor and are also found in extragonadal sites such as the pineal region, suprasellar region, mediastinum, and retroperitoneum.

Clinical presentation depends on location. Intracranial germinomas commonly cause headaches, nausea, and signs of increased intracranial pressure. Pineal-region tumors may lead to Parinaud syndrome, while involvement of the hypothalamic-pituitary axis can cause diabetes insipidus and endocrine disturbances. Serum and cerebrospinal fluid markers are often normal for alphafetoprotein, while beta-hCG may be mildly elevated in some cases due to syncytiotrophoblastic components.

Diagnosis is confirmed by histology. Germinomas show sheets of large, uniform cells with clear cytoplasm and prominent nuclei, set in a lymphocyte-rich background. Immunohistochemistry typically shows positivity for placental alkaline phosphatase (PLAP), OCT3/4, and often CD117 (KIT). Radiologic evaluation, especially MRI, usually reveals a midline mass in the pineal or suprasellar region with homogeneous enhancement; hydrocephalus may be present.

Treatment and prognosis: Germinomas are highly radiosensitive. Traditional management used craniospinal irradiation with a tumor boost, but many centers now employ chemotherapy (for example, platinum- and etoposide-based regimens) followed by reduced-dose radiotherapy to minimize late effects. Localized intracranial disease has excellent cure rates, with 5-year survival commonly exceeding 90%. Prognosis is more guarded with disseminated disease or nonintracranial, extragonadal presentations.