Chondroid Differentiated Metaplastic Carcinoma of the Breast: A Case Report and Review of the Literature

Metaplastic carcinoma of the breast is an uncommon and heterogeneous malignancy, accounting for less than 1% of invasive breast cancers. It is defined by the coexistence of epithelial and mesenchymal elements, occasionally with chondroid differentiation, which makes diagnosis challenging. We report the case of a 66 year old postmenopausal woman presenting with a firm right breast mass and mild nipple retraction. Imaging revealed a BI RADS 5 lesion. Core biopsy showed invasive carcinoma with a chondroid component, consistent with metaplastic carcinoma. Immunohistochemistry demonstrated strong positivity for estrogen (80%) and progesterone (70%) receptors, HER2 negativity, and a Ki 67 index of 30%. This hormone receptor–positive profile is rare in metaplastic carcinoma, which is usually triple negative, but may offer a therapeutic advantage with endocrine therapy. The absence of distant metastases at diagnosis further supports a favorable outlook. This case emphasizes the importance of accurate histopathological evaluation and a multidisciplinary, individualized management strategy for this rare breast cancer subtype.