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There is a cystic lesion with an enhancing mural nodule in the right cerebellar hemisphere abutting the right middle cerebellar peduncle. The cystic component is hyperintense on T2, incompletely suppresses on FLAIR with a medial enhancing mural nodule. The enhancing nodule demonstrates elevated CBV. The lesion projects into the fourth ventricle which is partially effaced inferiorly, though there is no evidence of upstream hydrocephalus or transependymal edema. There is T2/FLAIR hyperintensity extending into the right cerebellar hemisphere and vermis. There is no abnormal diffusion restriction associated with the cerebellar lesion.
In addition, there is a small left 6 mm intracanalicular enhancing nodule.
No other intra or extra-axial abnormality.
Cystic lesion with enhancing mural nodule has imaging features of a hemangioblastoma, with differential diagnosis of cystic metastasis. Intracannalicular nodule appears to be a vestibular schwannoma although the coincidence of the two lesions is difficult to reconcile into a unified diagnosis.
The patient went on to have a resection.
Sections show pieces of a somewhat circumscribed tumor composed of abundant small thin-walled capillary sized blood vessels. The intervening stroma contains epithelioid-to-stellate cells with bland nuclei and vacuolated cytoplasm. There is no necrosis, mitoses or atypia seen. A piece of the cerebellum is also included in the biopsy.
IMMUNOHISTOCHEMISTRY: The tumor cells stain positively in a patchy distribution for inhibin. The tumor cells are negative for Cam5.2 and Pax8.
FINAL DIAGNOSIS: hemangioblastoma (WHO Grade I).
The intercanalicular lesion has been followed and has not significantly changed in size. At this stage, it is presumed to be a schwannoma although the simultaneous diagnosis is unnerving.