Description
Retinal haemangioblastoma, also known as retinal capillary haemangioblastoma or von Hippel tumour, is a benign vascular tumour of the retina. It is typically associated with Von Hippel-Lindau (VHL) disease, a rare, autosomal dominant neoplastic disorder, although it can also occur sporadically.
Pathogenesis
The pathogenesis of retinal haemangioblastoma involves mutations in the VHL tumour suppressor gene located on chromosome 3p25-26. The VHL protein plays a crucial role in cellular oxygen sensing and angiogenesis. Mutations in the VHL gene result in overproduction of vascular endothelial growth factor (VEGF), leading to angiogenesis and the formation of highly vascularised tumours like haemangioblastomas.
Epidemiology, Risk Factors & Associations
Retinal haemangioblastomas occur in about 50-60% of individuals with VHL disease. They usually manifest in the second or third decade of life and may be the first sign of VHL disease. In the absence of VHL disease, they are exceedingly rare.
The main risk factor for retinal haemangioblastoma is a germline mutation in the VHL gene. Sporadic cases are rare and typically lack VHL mutations.
Clinical Features
- Visual disturbances: Depending on the location and size of the tumour, patients may present with vision loss, visual field defects, or floaters.
- Retinal detachment: Due to the exudative nature of the tumour, secondary retinal detachment may occur.
- Vitreous haemorrhage: Given the high vascularity of the tumour, spontaneous vitreous haemorrhage can occur.
Complications
Possible complications of retinal haemangioblastoma include retinal detachment, vitreous haemorrhage, neovascular glaucoma, and blindness.
Pathological Features
Histopathology
Histologically, retinal haemangioblastomas are composed of an abundance of thin-walled, dilated blood vessels interspersed with stromal cells.
Genetics
Patients with VHL disease carry germline mutations in the VHL gene.
Radiological Features
General Features
- Retinal haemangioblastomas present as well-circumscribed, round or oval retinal masses with prominent feeder vessels.
- Vitreous haemorrhage and retinal detachment may be present
MRI
- T1-weighted images: Lesions appear as well-circumscribed intraocular lesions that are isointense or slightly hypointense compared to the vitreous body.
- T2-weighted images: Lesions are hyperintense due to their high fluid content, sometimes with a central area of lower signal intensity due to flow voids or calcifications.
- Contrast-enhanced T1-weighted images: Strong, homogeneous enhancement after administration of gadolinium contrast.
CT
- Non-contrast CT: Hemangioblastomas are typically hypodense or isodense to the surrounding retinal tissue. Calcifications can be seen in some cases, appearing as high-density foci.
- Contrast-enhanced CT: These tumours demonstrate strong and homogeneous enhancement following iodinated contrast administration. The enhancement is due to the high vascularity of the tumour.
US
- Tumours appear as solid, dome-shaped or lobulated, highly reflective introcular masses
- Retinal detachment as a mobile, reflective echo
- Diffuse echogenic material in vitreous haemorrhage cases
Diagnosis
The diagnosis of retinal haemangioblastoma is based on characteristic clinical and imaging features. Biopsy is generally not performed due to the risk of haemorrhage.
Differential Diagnosis
Differential diagnoses include retinoblastoma, Coats disease, choroidal melanoma, and other vascular or exudative retinal lesions.
Management
Management options include laser photocoagulation, cryotherapy, plaque radiotherapy, or vitreoretinal surgery, depending on the size, location, and associated findings. In patients with VHL disease, regular screening and early treatment of retinal haemangioblastomas are essential to preserve vision.