OBJECTIVETo study the radiologic and pathologic features of primary intermediate hemangioendothelioma of the bone.

METHODSFive cases of primary intermediate hemangioendothelioma of bone encountered in the past three years were enrolled into the study. The clinical, radiologic, pathologic and immunohistochemical features of the tumors were reviewed.

RESULTSThe patients included 3 children with Kaposiform hemangioendothelioma and 2 elderly with retiform hemangioendothelioma. Four of the cases affected long bones and the remaining case affected the clavicle. One case showed multifocal involvement of the humerus. Radiologically, the tumors showed borderline to low-grade bony destruction, with various degrees of cortical defect. Intralesional or perilesional bone formation was demonstrated in 4 cases and radial spicules were seen in 1 case. The histopathologic features of primary intermediate hemangioendothelioma of bone were similar to those of soft tissue, except for the presence of reactive bone formation. Immunohistochemically, the tumor cells were positive for CD31 (5/5), CD34 (5/5), vimentin (5/5) and smooth muscle actin (3/5) but negative for cytokeratin and epithelial membrane antigen.

CONCLUSIONSPrimary intermediate hemangioendothelioma of bone is a distinct entity and similar histologic classification applies as in its soft tissue counterparts. Comparison of the biologic behavior requires long-term follow-up studies.