The patient went on to have a resection.

Histology

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.

Microscopic Description

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