Multimodality imaging and histopathology of metaplastic breast cancer.

Metaplastic breast cancer (MBC) is a rare subtype of invasive breast cancer characterized by mixed epithelial and mesenchymal differentiation. Commonly seen subtypes include squamous cell carcinoma, spindle cell carcinoma, and metaplastic carcinoma with heterologous mesenchymal differentiation. MBC tends to have a more aggressive clinical presentation, higher metastatic potential, higher rates of local recurrence, and a worse prognosis compared with invasive breast carcinoma of no special type. Most MBCs are triple-negative breast cancers, which explains their resistance to most systemic therapies. Therefore, accurately diagnosing MBC early is crucial for deciding the treatment strategy and predicting the prognosis. In this pictorial essay, the imaging findings of MBC in different modalities and the histopathologic features of its subtypes are reviewed.