RESUMEN
Squamous metaplasia of the breast ductal epithelium is a well-documented lesion; however, it represents a very uncommon histopathologic finding. We present a case of primary florid squamous metaplasia of the mammary ducts closely simulating a breast carcinoma in a 67-year-old woman. Patient after ultrasound examination and mammography, was submitted to a fine-needle aspiration biopsy (FNAB) that was considered inconclusive, and, in order to suspicious clinic and mammographic findings, a frozen evaluation during the surgical excision was performed. Primary squamous cell metaplasia is rarely observed in the breast. This condition closely mimics a malignant lesion at US-scan, X-ray evaluation and even at FNAB. Frozen examination, in this case, is considered decisive, preserving the patient from an unnecessary aggressive surgical approach.