Metastatic malignant pleural mesothelioma to the breast.

A 51-year-old woman suffered from dyspnea for several days before she came to an outside clinic for help. Pleura biopsy was performed and the histologic diagnosis was malignant mesothelioma. Sixteen months later, a palpable left breast lump was noted. Physical examination revealed a firm mass in the breast, measuring about 4 x 3.5 cm in size. Breast sonography showed a hypoechoic mass about 3 x 2 x 1.5 cm in size with irregular border in the middle part of the left breast. A mammogram revealed a speculated mass. Chest computed tomography was also performed, which revealed a large pleural mesothelioma and an irregular breast lesion. Incisional biopsy of the left breast lump was performed and histologic examination revealed an infiltrative growth of neoplastic polygonal cells bearing hyperchromatic and pleomorphic nuclei and a small amount of pale, pinkish cytoplasm. Further immunohistochemical study was performed and the tumor cells were positive for low and high molecular weight cytokeratin, thrombomodulin and focally positive for CEA. The final histologic diagnosis was metastatic malignant mesothelioma.