Breast cancer or metastasis? An unusual case of metastatic malignant pleural mesothelioma to the breast

Abstract

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.

Figure 1

Hematoxylin and eosin stain (H&E; 96 × 96 dpi). Infiltrative growth of neoplastic polygonal cells bearing hyperchromatic and pleomorphic nuclei with large eosinophilic nucleolus and a small amount of pale, pinkish cytoplasm.

Figure 2

Immunohistochemical stainings (96 × 96 dpi). (a) For calretinin, (b) for cytokeratin 8, (c) for cytokeratin 5/6, and (d) for HBME-1 (avidin-streptavidin-peroxidase-DAB).

Figure 3

CT of the chest (96 × 96 dpi). Sagittal reformatted CT image demonstrates the presence of a parenchymatous neoformation (6 cm) in the right parietal pleura (white arrow) and of another mass in the right axillary extension (3 cm) (black arrow).