Epithelioid and retiform hemangioendothelioma of the skull bone--report of four cases.

Hemangioendothelioma (HE) is a borderline or intermediate type of vascular neoplasm. We report clinical and histopathological characteristics of four cases of HE arising from the skull bones because of its extreme rarity in this location. The age of the patients ranged from 6-45 years. Three patients presented with a painless swelling over the head and one case had sphenoid wing mass with dimness of vision and proptosis. Radiographic images showed a well-demarcated, osteolytic lesion in the skull bone in all the four, one case in addition had sclerotic edges and another had specks of calcification. Grossly, the tumour was very vascular with hemorrhagic areas. Histologically, three cases showed features of an epithelioid variant of HE, with short strands and solid nests of rounded to slightly spindled, eosinophilic endothelial cells, some of them having small intracellular vacuoles. The stroma was myxoid--hyalinised with focal mixed inflammatory infiltrate. One case had features of a 'retiform' histological variant composed of numerous elongated vessels lined by a single layer of hobnail endothelial cells, focal lymphocytic infiltrate and papillae with hyaline collagenous cores. The tumour cells in all the four were immuno-labelled by antibody to factor VIII-associated protein. The tumour cells lacked cytological atypia and mitosis was sparse. These features were important in prognostication as low-grade tumours can be cured by complete wide-resection.