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A sizeable lobulated mass in the region of the pineal gland (3.2 x 3.1 x 3.5 cm) is present which has intermediate signal on both T1 and T2 weighted sequences, heterogeneous relatively limited contrast enhancement, prominent restricted diffusion (ADC = ~500mm2/s) and hypodensity on CT. The mass encases the internal cerebral veins (particularly in the right internal cerebral vein which courses through the middle of the mass). The mass is clearly separate from the vermis, with the superior vermian vein visible between it and the cerebellum. It is inseparable from the tectal plate, without high signal however extending into the midbrain. No separate pineal gland or pineal calcification can be identified.
The ventricles are enlarged with some transependymal oedema, and bowing of the recesses of the 3rd ventricle in keeping with hydrocephalus.
The remainder of the brain is unremarkable. No other areas of abnormal contrast enhancement are evident. Specifically no evidence of leptomeningeal seeding, and no abnormal enhancement in the floor of the 3rd ventricle.
Features are those of a highly cellular tumour encasing the internal cerebral veins arising from the pineal region. By far the most likely diagnosis is that of a high grade pineal parenchymal tumour (e.g. pineoblastoma). Low ADC values make a germinoma substantially less likely.