Presentation
A patient with 26 weeks of gestation presented with a progressive headache.
Patient Data
Left posterior fossa infratentorial extra-axial mass elicits low T1 and high T2 signals with small intra-tumoral cysts and multiple signal voids in enlarged vessels. Following contrast administration, it showed vivid contrast enhancement. No diffusion restriction on diffusion-weighted images (DWI). The mass is surrounded by peritumoral edema. It exerts a significant local mass effect with tonsillar herniation, compression of the 4th ventricle, and subsequent mild supratentorial hydrocephalus.
Conclusion:
Findings are suggestive of left posterior fossa hemangioblastoma.
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 caliber 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 hemorrhage 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.
Case Discussion
The patient went to urgent surgery for the excision of the mass via the suboccipital craniectomy approach. The diagnosis of hemangioblastoma was made by histopathology. Following surgery, the patient had an uneventful recovery with improvement in her neurological symptoms. She delivered a healthy baby at 38 weeks of gestation by cesarian section. The patient had a CT scan of the neck, chest, abdomen, and pelvis, which were unremarkable. Negative family history of Von-Hipple disease. Genetic testing showed an absent mutation in the VHL tumor suppressor gene.
Cerebellar hemangioblastomas are benign WHO-grade I tumors of vascular origin. Approximately 80% of hemangioblastomas occur sporadically, with the remainder (20%) developing in patients with von Hippel-Lindau disease. Sporadic lesions are usually single and large, while VHL-associated hemangioblastomas are usually small and multiple. Hemangioblastomas may be cystic, solid, or mixed. Solid hemangioblastomas could mimic posterior fossa neoplasms, especially metastasis.
The incidence of hemangioblastoma of the posterior fossa in pregnancy is extremely low 1. Hemangioblastomas may demonstrate a rapid increase in size during pregnancy, and patients may present with features of increased intracranial pressure caused by obstructive hydrocephalus in addition to cerebellar and brainstem compressive features; hence, they may require urgent surgical therapy. Various hypotheses were proposed to explain the rapid neurological deterioration of hemangioblastoma patients during pregnancy, including rapid expansion or engorgement of the vascular bed secondary to an increase in blood volume occurring during pregnancy 2. The other hypotheses are direct hormonal effects on tumor growth rate, mediated by hormonal receptors 3.
Typical radiological features include a high T2 signal, facilitated diffusion, vivid enhancement, small intra-tumoral cysts, and surrounding prominent vessels.
DDx: solid hemangioblastomas can mimic meningiomas, metastasis, or medulloblastomas.
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