Multicentric contiguous variant of epithelioid angiosarcoma of the bone. A rare variant showing angiotropic spread.

Epithelioid angiosarcoma of the bone is a rare tumor and is a diagnostic challenge. Here we present an autopsy case of a 62-year-old man with multifocal osteolytic lesions in the extremities and the pelvis. The initial diagnosis of a tibial biopsy was poorly differentiated adenocarcinoma. On the occasion of autopsy, a fungating thrombotic nodule was found at the anterior wall of the right atrium, and small hemorrhagic infarcts with tumor thrombi were found in the lung. Histologically, the above lesions were identical to the former tibial biopsy and they showed large eosinophilic epithelioid cells with irregular ovoid nuclei and prominent eosinophilic nucleoli. Rare intracytoplasmic lumina were identified. Immunohistochemically, the tumor cells were positive for cytokeratins (CAM5.2 and AE1/AE3), CD31, factor VIII-related antigen, and vimentin. This case showed angiotropic spread of the tumor only to the right atrium and the lung, with no solid mass in other organs. Multicentric epithelioid angiosarcoma of the bone is a pitfall in pathological diagnoses, especially if a strong radiological impression of metastatic carcinoma is provided. Therefore, pathologists should be aware of this rare variant.