PET/CT of Germinomas

Abstract

Intracranial germinomas are mostly located adjacent to the midline structure, 80–90% in the midline, 1/2–2/3 in the pineal region, 1/4–1/3 in the suprasellar region, and 5–10% in the basal ganglia region. The size of germinomas varies depending on their location. The germinoma in the pituitary stalk can cause symptoms when it is very small, while that in the pineal region can grow to a large size if not causing hydrocephalus by invading the tectum and the central canal. About 20% of intracranial germinomas are multifocal and usually occur simultaneously in the pineal region and the suprasellar region. Germinomas are generally solid tumors and brittle in consistency and can infiltrate adjacent tissues. Intratumoral cystic changes, small focal hemorrhage, and cerebrospinal fluid spread are commonly seen. Mitosis is common in germinomas, but necrosis is rare.