Background: Metastases to the breast from extramammary malignancies are very rare, and ruling out the
diagnosis of primary breast tumor is important in order to decide on clinical management and predict prognosis.
Case presentation: Clinical examination revealed in a 49-year-old hairdresser a 3-cm hard lump adherent to
the underlying layers in the right breast. Trucut biopsy was performed. Histology showed a solid proliferation of
medium-sized neoplastic polygonal cells. Immunohistochemical analysis showed tumor cells diffusely positive for
cytokeratin 8/18 and calretinin and focally positive for cytokeratin 5/6 and Wilms’ tumor 1, e-cadherin, and human
bone marrow endothelial-1. Estrogen receptors and progesterone receptors were negative. The final diagnosis was
metastatic epithelioid malignant pleural mesothelioma.
Conclusions: Immunohistochemistry is an important tool for a conclusive diagnosis of malignant pleural
mesothelioma. Owing to the degree of histological and immunohistochemical overlap, a high level of clinical
suspicion is essential in order to avoid unnecessary mutilating surgery