The patient went on to have a resection.
Histology
Histopathological examination of the mass revealed a discrete neoplasm that, at low magnification, shows high vascularity with prominent, large, thin-walled vessels. The cellularity is variable, with some architecturally loose areas and others that are more crowded and compact. At high magnification, the neoplasm is formed of two principal intermingled components: vascular elements and interstitial stromal cells. The calibre of the vessel channels is predominately capillaries. Stromal cells show eosinophilic cytoplasm, which is variably lipidized and vacuolated, together with mainly pleomorphic hyperchromatic nuclei. Scattered mitotic figures are noted. Many hyaline globules are detected. Areas of haemorrhage and cerebellar tissue are seen.
Immunohistochemistry
Inhibin A: Positive staining of the neoplastic stromal cells confirms the diagnosis of hemangioblastoma.
EMA, pan CK: negative staining of neoplastic cells. Adjacent cerebellar tissue and entrapped astrocytes show positive staining.
Ki-67: the proliferation index in neoplastic cells is around 12% to 15% (N.B.: Hemangioblastoma occasionally shows elevated Ki-67 proliferation indices).
Final diagnosis
Histopathologic and immunohistochemical features are compatible with hemangioblastoma WHO grade 1.