Germinoma
The Common Vein Copyright 2010
Definition
A germinoma is a tumor of the germ cell line which is most often located in the gonads, but can be found in multiple extragonadal locations. Intracranially they tend to be in the pineal region, making up approximately 40% of pineal region masses, however they may also be located elsewhere including the suprasellar region and less frequently the basal ganglia. The exactly etiology is unknown. It generally presents in adolescents or young adults. These masses are locally infiltrative and may result in CSF dissemination.
Pathologically germinomas are characterized by sheets of cells with a high nuclear to cytoplasmic ratio surrounded by fibrous connective tissue. Mitotic figures may be present.
Clinically patients with pineal region germinonas may present with what is called Parinaud’s syndrome, or pareseis of upward gaze caused by compression of the dorsal midbrain. Symptoms of hydrocephalus may also occur due to obstruction of the aqueduct of Sylvius. Visual loss, endocrinopathy and diabetes insipidus are presenting symptoms of suprasellar germinomas.
Diagnosis can be suggested by imaging findings however should be made by tissue sampling and pathologic analysis.
Imaging includes CT and MRI. Characteristically these tumors are homogeneous hyperdense masses on CT. If calcifications are seen they are centrally located because they are thought to be with in the pineal gland tissue which is engulfed by the germinoma. Cystic components can infrequently be seen. On MRI they are intermediate on T1 and relatively low signal on T2. Due to their high cell count, they often show high signal on diffusion weighted images with low ADC map corresponding signal. After contrast, these masses enhance avidly. Due to their propensity for CSF dissemination, imaging of the entire neuroaxis is suggested.
Treatment includes radiation with possible chemotherapy. These patients have a high