Tot T. Metastatic chordoma of the breast: an extremely rare lesion mimicking mucinous cancer. APMIS 2006;114:726–9. 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.