Metastatic chordoma of the breast: an extremely rare lesion mimicking mucinous cancer.

Metastases in the breast are rare, with metastatic chordoma being one of the rarest. To our knowledge, only one such case has previously been published in the literature. We report a case of a 74-year-old woman who presented with a palpable lump in her right breast. The lump was mammographically suggestive of mucinous breast cancer because it was a solitary, small, circular, and moderately dense lesion yielding abundant mucoid aspirate. The tumor resembled mucinous carcinoma upon histologic and immunohistochemical examination: it had a mucinous stroma, and the tumor cells strongly expressed epithelial markers. However, the patient had previously undergone surgery for a recurrent sacral chordoma. In addition to the clinical history, the presence of typical physaliferous cells expressing neither estrogen receptors nor cytokeratin 7, but staining positively for S-100 protein, allowed the proper diagnosis. Although extremely rare, metastatic chordoma may represent a challenge in the differential diagnosis of breast lesions. Discriminating metastases of mucin-producing tumors in the breast from primary mucinous carcinomas is important with regard to the striking difference in prognosis of these lesions.