Presentation
2 weeks of headaches.
Patient Data
A sizable 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 edema, 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.
Conclusion:
Features are those of a highly cellular tumor encasing the internal cerebral veins arising from the pineal region. By far the most likely diagnosis is that of a high grade pineal parenchymal tumor (e.g. pineoblastoma). Low ADC values make a germinoma substantially less likely.
The sections show a densely cellular tumor. It forms diffuse sheets as well as some perivascular pseudorosettes. Homer-Wright rosettes are absent. The tumor cells have increased N/C ratio with enlarged round nuclei, small nucleoli and scanty cytoplasm. There is no nuclear molding. Small numbers have shrunken nuclei. No necrosis is seen. There are about 10 mitoses per 10 high power fields. The tumor cells are synaptophysin positive. There is very focal staining for neurofilament. The Ki-67 index is about 20%. GFAP and EMA are negative.
FINAL DIAGNOSIS:
Pineal parenchymal tumor with intermediate differentiation (WHO Grade III).
Case Discussion
Try as one might, sometimes pathologists just split diagnoses too much to allow for accurate pre-op diagnosis. In this case the tumor was indeed a pineal parenchymal tumor, but did not quite make it to a pineoblastoma, rather only a pineal parenchymal tumor with intermediate differentiation (WHO Grade III).
The location of the internal cerebral veins running through the tumor precluded safe complete excision.
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