Discussion
EHE is a rare low grade malignant neoplasm with potential for metastasis. Only 20% of the cases present with metastasis1.,5. It originates from vascular endothelial or pre-endothelial cells. Although it can develop anywhere in the body it most reported in the liver, lungs and bone. Primary EHE of the bone is rare constituting only 1% of all malignant tumours of the bone1,2,5., as such primary involvement of the spine in EHE is very rare 5. Spinal EHE has a non-specific clinical presentation, usually with pain (mostly radicular or mechanical in nature) or neurological deficits attributable to compression of the spinal cord and/or nerve roots. There is a paucity of literature on EHE in Africa with only a few case reports on pulmonary, hepatic and pleural EHE and none for primary EHE of the Spine6,7. It occurs equally in both males and females with no racial predilection1.Weissferdt et al describes better overall survival for unicentric tumour as compared to multifocal disease (89% and 50% respectively) and a mortality rate of 20%. The median survival is at 1.3 years and 5-year survival of 33% after disease progression5.
Although EHE of the spine has no pathognomic features that are specific enough to be used as the sole means of diagnosis, most if not all cases show an expansile osteolysis with bony trabeculae and lack a sclerotic margin. There is usually vertebral body collapse with segmental kyphotic deformity1,2,3,4,5. On MRI the lesions are usually isointense to grey mater on T1 weighted imaging, slightly hyperintense on T2 weighted imaging with increased uptake of contrast on contrasted sequences1. Chen P et al., suggests that18F-FDG PET/CT scan may be of some use in difficult cases (especially those with multifocal disease) with hypermetabolism, but this is not pathognomic and as such cannot be used in solitude to confirm diagnosis of EHE or its dissemination2.
Macroscopically the tumour a reddish-brown mass with tendency to bleed. The diagnosis of EHE rests mostly on the histopathological analysis. Microscopically the tumour cells appear as round, polygonal or fusiform with a central nucleus and intracytoplasmic vacuolations but with the absence of increased mitotic activity or necrosis2,3,4,5,8. Immunohistochemically EHE stains positive for CD31, CD34, EGR, Factor VIII related antigen and FLI-12,3,4,5,8. Cytogenetic analysis can be used to show chromosomal translocation involving chromosomes 1 [t(1;3) and 3 (p36.3;q25) that results in WWTRI-CAMTAI fusion. This is present in approximately 90% of the cases with EHE2,3. A subset of patients with EHE may show YAP-1 TFE 3 fusion10.
The mainstay of treatment for patients with EHE of the spine seems to be multimodal with surgery, total resection where feasible, as the centrepiece.2,3,5 Pre-operative embolization to reduce the vascularity of the tumour and radiation and chemotherapy are also described. Given the rarity of EHE, especially EHE of the spine, there currently exists no universally accepted treatment guidelines with clearly defined outcomes.