Metaplastic squamous cell carcinoma of the breast: A case report and literature review.

Metaplastic tumors are rare and represent a heterogeneous group of neoplasms showing dominant areas of non-glandular differentiation. Etiology and pathogenesis of this type of lesion in the breast is uncertain. The most common sources of metastatic squamous cell carcinoma of the breast are lung, esophagus, cervix, and urinary bladder.