A Rare Tumor that Mimicked Metastasis in a Patient with Breast Cancer: Epithelioid Hemangioendothelioma.

A woman aged 50 years was diagnosed as having an invasive ductal carcinoma in the right breast and ductal carcinoma in situ in the left breast and underwent bilateral mastectomy eight years ago. A mass was identified during follow-up in positron-emission tomography (PET) image in the left infraclavicular region, indicating metastasis. Histopathologic examination showed a mass of 1.9 × 1 × 0.7 cm in dimensions characterized by spindle or round nuclei cells that formed island or cords in hyaline and myxoid ground and intracytoplasmic vacuoles containing erythrocytes. In the immunohistochemical analysis, tumor cells were widespread with diffuse positivity with CD34 and vimentin. These findings redirected us from a diagnosis of metastatic carcinoma to epithelioid hemangioendothelioma, a rare tumor of intermediate vascular tumor groups. In this respect, confirmation through biopsy from considered cases of metastasis is important in making a definite pathologic differential diagnosis.