- 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.