Haemangioblastoma

Haemangioblastoma is a rare, benign, highly vascular neoplasm typically arising in the cerebellum and characterised by brightly enhancing nodules surrounded by a cyst on imaging.

Description

Haemangioblastoma is a rare, benign vascular neoplasm of the central nervous system. It is typically associated with Von Hippel-Lindau (VHL) disease but can also occur sporadically. Haemangioblastomas are most commonly found within the cerebellum but can occur anywhere along the neuroaxis. It represents the most common primary tumour within posterior fossa in middle-aged/older adults (but not the most common posterior fossa intra-axial mass, which is metastasis).

Pathogenesis

Haemangioblastomas are hypothesised to originate from multipotent mesenchymal stem cells. Mutations in the VHL gene (chromosome 3p25-26), particularly in cases associated with Von Hippel-Lindau disease, lead to upregulation of vascular endothelial growth factor (VEGF), promoting vascular proliferation and the formation of highly vascularised tumours.

Epidemiology, Risk Factors & Associations

• More common in adults, with peak incidence between 30 and 50 years.
• Single tumours are usually sporadic and non-syndromic.
• Multiple tumours are usually associated with Von Hippel-Lindau disease (up to 25% of cases).
  • Multiple renal cell carcinomas (clear cell type)
  • Adrenal pheochromocytoma
  • Solid organ cystic lesions (hepatic cysts, pancreatic cystadenomas)
• Associated with secondary polycythaemia due to erythropoietin production

Clinical Features

Patients often present with symptoms related to increased intracranial pressure (headache, nausea, vomiting) and local mass effect (ataxia, vertigo). In cases associated with VHL disease, patients may also have retinal angiomas, renal cell carcinomas (clear cell subtype), or pheochromocytomas.

Complications

• Obstructive hydrocephalus due to tumour location.
• Neurological deficits depending on the tumour location.
• Haemorrhage due to the highly vascular nature of the tumour.

Pathological Features

Histopathology

• Macroscopic: Haemangioblastomas are well-circumscribed, reddish-pink tumours due to their high vascularity.
• Microscopic: Characterised by a proliferation of small capillaries with intervening stromal cells resembling foamy cells.

Haematology

• Features of associated secondary polycythaemia may be seen:
  • Elevated haemoglobin, haematocrit, and red blood cell count, normal or elevated erythropoietin levels
  • Normal white blood cells and platelets

Serology

No specific serological markers.

Biochemistry

No specific biochemical markers.

Radiological Features

General Features

• Typically a well-defined mass with a cystic component and a vividly enhancing mural nodule (60%)
• Other appearances include a predominantly solid mass with no cystic component (40%)
• Calcifications are rare, observed in less than 5%
• Murphy’s Trifecta sign: mural nodule, large cyst, and surrounding oedema.
• Typical locations:
  • Intracranial
    • 95% infrantentorial compartment (posterior cranial fossa)
      • Cerebellar hemisphere (85%)
      • Cerebellar vermis (10%)
      • Medulla (5%)
    • 5% supratentorial brain
  • Spinal

CT

• Non-contrast: Hypodense or isodense mass with a hyperdense cystic component.
• Contrast-enhanced: Intense enhancement of the mural nodule.

MRI

• T1: Hypointense or isointense mural nodule with hypointense cystic component. High T1 signal suggests fat or haemorrhage.
• T2: Hyperintense cyst matching CSF intensity. Mural nodule may be hyperintense. Flow voids present (60-70%).
• T1 C+: Vivid enhancement of the mural nodule. Cyst wall does not enhance.
• DWI/ADC: No restricted diffusion.

Grading and Staging

Haemangioblastomas are WHO Grade I tumours. No specific staging system exists for these lesions as they are benign.

Diagnosis

Diagnosis requires a combination of clinical presentation, radiological features, and histopathological confirmation post-surgery.

Differential Diagnosis

• Metastasis: Characteristically demonstrates multiple lesions in a patient with known malignancy. MRI may show surrounding vasogenic oedema.
• Pilocytic Astrocytoma: Typically a paediatric tumour, may also have a mural nodule with a cystic component. The mural nodule may be larger and can show a similar enhancement but calcifications are more common compared to haemangioblastoma. No contrast blush of the mural nodule on angiography.
• Haemorrhagic or cystic Ependymoma: These can also appear as a cyst with a mural nodule, particularly in the spinal cord, but often show more irregular margins.

Management

Neurosurgical resection is the treatment of choice. Preoperative embolisation may be beneficial given the highly vascular nature of these tumours. Follow-up imaging is required to monitor for recurrence or new lesions, particularly in patients with VHL disease.