Synchronous Metaplastic Breast Carcinoma with Mesenchymal Differentiation and Triple-Negative Invasive Papillary Carcinoma: A Case Report and Literature Review

Background

Metaplastic breast carcinoma with mesenchymal differentiation is a rare and morphologically heterogeneous malignancy that may show a biphasic epithelial and sarcomatoid pattern historically termed “carcinosarcoma.” Its synchronous occurrence with invasive papillary carcinoma is exceptionally uncommon and may create diagnostic and therapeutic difficulties.