Hemangioblastoma

• HGBLs are benign, slow-growing, relatively indolent vascular neoplasms. 
• Multiple HGBLs are almost always associated with the autosomal-dominant inherited cancer syndrome von Hippel-Lindau disease (VHL). 
• A rare non-VHL form of multiple disseminated HGBLs is termed leptomeningeal hemangioblastomatosis.
• The cerebellum is by far the most common site (80%) followed by the vermis (15%). 
• Approximately 5% occur in the brainstem, usually the medulla. 
• The nodule of an HGBL is superficially located and typically abuts a pial surface.
• HGBLs contain two different cell types: Stromal and vascular cells. Generally it is the stromal (not the vascular) cells that are the neoplastic element of an HGBL.
• The cyst wall of most HGBLs is nonneoplastic, composed of compressed brain with fibrillary neuroglia devoid of tumor cells. 
• HGBL is a WHO grade I neoplasm.
• HGBL accounts for 1-2.5% of primary CNS neoplasms and approximately 7% of all primary posterior fossa tumors in adults. 
• It is the second most common infratentorial parenchymal mass in adults (after metastasis).
• HGBL is generally a tumor of adults between the ages of 30 and 65 years. 
• Pediatric HGBLs are rare. VHL-associated HGBLs tend to present at a significantly younger age but are still relatively rare in children under the age of 15. 
• Headache is the presenting symptom in 85% of cases.
• A nonneoplastic peritumoral cyst with solid nodule is the most common pattern, seen in 50-65% of cases. 
• CT - The most common appearance is a well-delineated iso- to slightly hyperdense nodule associated with a hypodense cyst. Calcification and gross hemorrhage are absent. The nodule enhances strongly and uniformly following contrast administration.
• MR - Cystic component is hypointense compared to brain on T1WI & hyperintense on T2WI. The mural nodule is usually isointense on T1 & hyperintense on T2WI. Prominent "flow voids" in the nodule are common. Intense enhancement of the nodule—but not the cyst itself—is typical.
• Angiography - The most common appearance is that of an intensely vascular tumor nodule that shows a prolonged vascular "blush".
• D/D - Older age - Metastasis; Younger age - Pilocytic astrocytoma, Cavernous malformation

Autopsy specimen shows nodule , hemorrhagic cyst  of a typical HGBL. 

T2WI shows classic HGBL with a hyperintense cyst , tumor nodule  abutting pial surface.

T1 C+ FS MR in the same patient shows that the tumor nodule  enhances intensely while the cyst wall does not.