A germ cell tumor is most often found initially on an MRI scan ordered after an individual experiences symptoms suggestive of a brain tumor. Once evidence a tumor is seen on a brain scan, the important next step is to determine its type so that the treatment can be tailored to that particular type of tumor.
Doctors will suspect a primary CNS germ cell tumor based on clinical findings (adolescent or young adult, vision changes, diabetes insipidus, and double vision) and an MRI scan showing a parasellar or pineal region mass. If a germ cell tumor is suspected, doctors should preferentially use non-surgical methods for establishing a diagnosis. Tumor biopsy and even removal is not needed in nearly half of patients with intracranial germ cell tumors. In fact, germ cell tumors are the only type of brain tumors that can be diagnosed with simple blood tests. When a germ cell tumor is suspected, doctors test blood (and, when possible, cerebrospinal fluid) for the tumor markers human chorionic gonadotropin (HCG) and alpha (α) fetoprotein (AFP). Blood and CSF sampling for intracranial germ cell tumor markers should always be done before tumor biopsy. The elevation of any of these tumor markers is enough to initiate a plan of treatment using chemotherapy without the need for surgical biopsy. Marker negative or biochemically silent tumors will require biopsy for confirmation.
Based on tumor markers, germ cell tumors are classified as non-germinomatous germ cell tumors (NGGCT) or pure germinoma. Almost half of intracranial germ cell tumors, however, are classified as mixed malignant GCTs, since they have features of both. All types of CNS GCT can have an excellent outcome, with germinoma having a 90 percent cure rate and NGGCT ranging from 50 to 75 percent.
Because of the complexity and rarity of these tumors, highly experienced neurosurgeons are an integral part of the initial decision making and treatment team. Importantly, including an experienced neurosurgeon in the initial evaluation may avoid unnecessary surgery and its inherent risks.
Reviewed by Mark M. Souweidane, MD
Last reviewed/last updated: December 2020