Specific Imaging Findings

CT of pineal germinomas shows the masses centered at the pineal gland to be slightly hyperdense without contrast, contain a central or peripheral characteristically intact calcification (so-called “engulfed” pineal calcification) and show dense contrast enhancement. Cysts are not uncommon, particularly if the tumor is big, while hemorrhage is rare. The tumors are isointense to brain on T1-weighted images, of isointense to low T2 signal and with ADC values similar to the brain on diffusion imaging. After gadolinium, these tumors show marked enhancement. Another common location for germinomas is the suprasellar region, where they exhibit the same imaging features. It is important to evaluate the entire craniospinal axis after contrast has been given to look for CSF tumor spread. MR spectroscopy shows high choline, low NAA and lactate.

Pertinent Clinical Information

Over 90% of germinomas are found in patients aged under 20 years (peak ages: 12–20 years). Those in the pineal gland are more common in males and the usual clinical findings include: Parinaud syndrome and signs of increased intracranial pressure. Those arising in the suprasellar region produce diabetes insipidus, vision abnormalities and precocious puberty. There is an increased incidence of germinomas in the following syndromes: Down, Klinefelter and neurofibromatosis type 1. Neuroendoscopic procedures are used for both lesion biopsy and management of hydrocephalus associated with these tumors. The risk of tumor dissemination following surgery is minimal when appropriate chemotherapy and radiotherapy are provided postoperatively. The tumors are very radiosensitive, a fact that contributes to a relatively good prognosis, with 10-year overall and progression-free survival in the range of 80–90%.