Epithelioid Hemangioendothelioma of Bone

Epithelioid hemangioendothelioma (EHE) is a rare, well-differentiated endothelial tumor with a wide spectrum of behavior. The term was designed to describe tumors that had an appearance in between hemangiomas and sarcomas. Epithelioid hemangioendothelioma has several synonyms: low grade anaplastic angiosarcoma, cellular hemangioma, histiocytoid hemangioma and angioendothelioma. It represents 1% of all vascular neoplasms and is locally aggressive.
     Epithelioid hemangioendothelioma occurs in the calvarium, spine, femur, tibia and feet of adults during the second or third decade. Multiple lesion may be present, either in the same bone (particularly in the tibia or fibula), in adjacent bones in the same limb, or in widely separated bones.  Nearby or distant soft tissues and skin may be involved as well, and metastases to the lung (or simultaneous primary lesions in the lung) have been reported in two cases.  It is more common in men than women and is found in the metaphysis or epiphysis. Clinically, epithelioid hemangioendotheliomas presents with pain and swelling. If present in the spine, a lesion may cause radicular symptoms or paraplegia.
     On radiological examination, epithelioid hemangioendotheliomas are expansive, osteolytic and poorly demarcated lesions. They have a distinctive "soap-bubble" matrix with a sclerotic margin. No periosteal reaction is present.  Lesions with particularly ill-defined margins and loss of trabeculae are considered more aggressive. CT scan findings are noncontributory as they only reflect soft-tissue density but lesions do enhance with contrast media.
MRI findings are also non-specific. The radiological differential includes metastatic carcinoma, Ewing's sarcoma, telangiectatic osteosarcoma, lymphoma, fibrous dysplasia and aneurysmal bone cyst.
     On gross examination, epithelioid hemangioendotheliomas are reddish-brown loculated masses with significant hemorrhage.
     Microscopically, epithelioid hemangioendotheliomas appear as irregular anastomosing vascular channels. The channels are lined by plump endothelial cells without pleomorphism or mitotic activity. Both the background stroma and the cells lining the vascular channels stain positive for reticulum. The epithelioid histological subtype of epithelioid hemangioendothelioma has epithelial like cells lining the vascular channels. The spindle cell variant has spindle cells separating the vessels. Various criteria are used to determine if the lesion is benign or malignant including the number of mitoses, hyperchromatic nuclei, pleomorphism and nucleus to cell ratio.
     The treatment of epithelioid hemangioendothelioma depends on the grade of the lesion. Benign appearing lesions may be treated with currettage, or wide resection where possible. Wide resection or (rarely) amputation are necessary for more aggressive tumors.  The role of radiation and chemotherapy is ill defined at this time. Epithelioid hemangioendotheliomas may metastasize to bone and lung. Prognosis in these rare instances has been variable but may be good.

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Perkins, P and SW Weiss, Spindle Cell Epithelioid hemangioendothelioma. The American Journal of  Surgical Pathology, 20(10):1196-1204, 1996.









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