RESUMEN
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. Squamous cell carcinomas may present clinically with inflammation and average size greater than breast adenocarcinoma. As for imaging studies, mammography shows no typical findings and ultrasound can show a complicated cyst or an inflammatory process, among the differential diagnoses. Therefore, knowing this pathological entity, its clinical course and imaging findings is important to safely treat such a rare and aggressive disease. We herein report a case of metaplastic carcinoma, squamous subtype, diagnosed by core needle biopsy.