Background: Epithelioid hemangioma (EH) is a rare benign vascular lesion of soft tissue and bone, characterized by endothelial cells with epithelioid or histiocytoid appearance. Though tubular bones, flat bones, vertebra and short bones are common sites for this lesion, the epiphyseal involvement is extremely rare. We present an unusual case of EH of the distal femur in a young boy.
Case report: A 12-year-old boy who had congenital talipes equinovarus of the right foot presented with progressively increasing pain in the right lower thigh for six months. Physical examination revealed muscular atrophy of the right lower limb and a moderately tender swelling in the medial aspect of the right knee without restriction of knee movement. An X-ray revealed an osteolytic lesion, which appeared iso- and hypointense on T1W and hyperintense on T2W MRI images in the distal epiphysis and adjacent metaphysis of the right femur. A radiological diagnosis of chondroblastoma was entertained. The patient was treated with curettage and bone grafting. Histopathology showed a tumor composed of thin-walled arteriolar capillaries lined by large, polyhedral epithelioid endothelial cells with vesicular nuclei, finely distributed nuclear chromatin, and moderate amount of eosinophilic cytoplasm. The endothelial cells were strongly immunopositive for CD34. Mitotic activity was low and the Ki-67 proliferative rate was <2%. A diagnosis of EH was made. EH is a benign lesion and it should be differentiated from its histologically similar malignant counterparts such as epithelioid hemangioendothelioma and epithelioid angiosarcoma as the lesion can be successfully treated with curettage or resection.