Epithelioid Hemangioendothelioma

Abstract

Epithelioid hemangioendothelioma (EHE) of bone is a rare, low- to intermediate-grade malignant endothelial neoplasm, characterized by a proliferation of epithelioid endothelial cells arranged in cords, nests, and sometimes well-delineated vascular structures enmeshed in a hyalinized, chondroid, or basophilic stroma. EHE can be seen in most age groups and has its peak frequency in the second decade of life. The tumor tends to arise in the extremities, pelvis, and spine and is frequently multicentric in a single bone or multiple bones simultaneously. Localized pain and swelling are presenting symptoms. Intracytoplasmic vacuoles, sometimes containing fragments of erythrocytes or intact erythrocytes, are characteristic (“blister cells”). A recurrent translocation resulting in a WWTR1-CAMTA1 gene fusion is identified in approximately 90% of cases, and nuclear expression of CAMTA1 by immunohistochemistry is a useful diagnostic tool. Wide en bloc surgical resection is the preferred choice of treatment, although this may not be feasible in multicentric disease. EHE of bone usually behaves in a relatively indolent fashion and, in the absence of parenchymal organ involvement, has a low rate of dissemination.