Multicentric epithelioid angiosarcoma of the bone. Pitfalls in clinical and morphological diagnosis.

Epithelioid angiosarcoma of the bone represents a challenging diagnosis by bone marrow biopsy. We present a case of a multicentric high grade angiosarcoma of the bone with epithelioid features. On the basis of the clinical presentation, the radiological findings, and the appearance of loosely clustered tumor cells detected in the initial bone marrow biopsy, the main differential diagnoses considered were a poorly differentiated non-secretory multiple myeloma and metastatic carcinoma. Subsequent morphologic, immunohistochemical and electron microscopic examination of tissue samples clarified the nature of the tumor as epithelioid angiosarcoma. We discuss potential pitfalls in clinical and morphological diagnosis. The strong reactivity of the tumor cells with the nonspecific but ubiquitous mesenchymal marker vimentin in similar cases should direct early attention to the rare malignant bone tumor, epithelioid angiosarcoma, with subsequent confirmation of this diagnosis with specific immunohistochemical endothelial cell markers and/or electron microscopy.