Metaplastic breast carcinoma with chondroid differentiation: a rare variant of infiltrative carcinoma in a 38-year-old woman.

Metaplastic breast carcinoma (MBC) is a rare type of invasive breast carcinoma, and chondroid differentiation is even rarer. Here we report a case of MBC with extensive chondroid differentiation in a 38-year-old woman who presented with a lump in her left breast. Ultrasound findings were most compatible with those of giant fibroadenoma. A histopathological examination revealed a malignant lesion comprising neoplastic epithelial cells arranged in solid nests, with large areas of chondroid differentiation. Neoplastic chondroid cells exhibited a positive reaction for S-100, patchy positive reaction for pan-cytokeratin (AE1/AE3) and negative reaction for epithelial membrane antigen. Both carcinomatous and chondroid cells exhibited p53 overexpression. Sentinel lymph node biopsy revealed no tumorous involvement.