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MRI of the posterior fossa of a young adult demonstrates a cystic mass in the superior aspect of the left cerebellar hemisphere. An excentric solid component is seen anterolaterally which is somewhat hypointense on T1 and hyperintense on T2 compared to adjacent brain. A minor degree of high T2 signal is seen surrounding the mass consistent with edema.
Following administration of contrast the solid component enhances vividly , with no evidence of enhancement of the cyst wall. Features are consistent with a hemangioblastoma of cerebellum. (confirmed histologically)
No other lesions are identified to suggest underlying von Hippel Lindau syndrome.
The patient went on to have a resection.
On sectioning of the larger specimen, it has an outer rim of dark red, friable tissue resembling clot with central soft red tissue resembling blood.
The sections show that the lesion is comprised of numerous thin-walled vessels. Between these vessels there are stromal cells, which have rounded nuclei. Some of the nuclei are hyperchromatic and large. No mitotic figures are seen. There is cerebellum, which shows atrophy as evidenced by rarefaction of the granular layer and loss of Purkinje cells. Granular PAS-positivity, removed by diastase digestion, is evident in stromal cells. The tumor shows numerous reticulin fibrils. Immunohistochemistry shows that the tumor is negative for glial fibrillary acidic protein, epithelial membrane antigen and keratin. There are numerous small-diameter CD31-positive vessels within the tumor.
FINAL DIAGNOSIS: hemangioblastoma