Report of a metaplastic carcinoma of the breast with multi-directional differentiation: an adenoid cystic carcinoma, a spindle cell carcinoma and melanoma.

Metaplastic carcinoma of the breast is a heterogeneous neoplasia, generally composed of both epithelial and mesenchymal components. We report an unusual case of mammary metaplastic carcinoma in a 51-year-old female patient. Needle core biopsy from the tumour mass showed malignant epithelial and sarcomatous features. The resection specimen revealed a multi-directional tumour differentiation consisting predominantly of: firstly, a poorly differentiated basaloid epithelial cell type, consistent with an adenoid cystic carcinoma; secondly, areas of a spindle cell carcinoma; and, thirdly, areas with a melanocytic differentiation. This is the first report on a metaplastic carcinoma of the breast presenting as an admixture of an adenoid cystic carcinoma and melanoma.