Squamous Cell Subtype of Metaplastic Breast Carcinoma: An Unusual Case

INTRODUCTION: Metaplastic carcinoma (MC) is a heterogenous group of malignant neoplasms containing both glandular and non-glandular components with mixed epithelial and mesenchymal differentiation. It’s an uncommon but often-aggressive breast cancer and can be challenging to differentiate from other types of breast cancer and even benign lesions based on the imaging appearance. CASE REPORT: The patient was a 62-year-old woman whose local examination showed a small- ulcerated lesion in lower inner breast quadrant (inframammary fold). A core-biopsy showed a squamous cell carcinoma. A resection was performed to elucidate the diagnosis. A triple-negative MC was found with squamous differentiation. Bone, chest and abdominal scans were performed before systemic therapy with no signs of metastatic disease. Neoadjuvand anthracyclines and taxanes-based chemotherapy was indicated with progression of disease during treatment (local, bones and liver). DISCUSSION: Due to its rarity and heterogeneity, there is no standard therapy for patients with MC. The spindle cell subtype is the most common of the 5 subtypes classified by Wargotz and Norris. The squamous cell carcinoma subtype demonstrates infiltrating squamous carcinoma with polygonal cells, eosinophilic cytoplasm, and possible keratin pearl formation. It is a very aggressive breast cancer type. Single institution retrospective studies and genomic profiling suggest that these tumors are largely chemoresistant. Clinical trials comparing standard therapies for Invasive Ductal Carcinoma in patients with MC are needed, but are unlikely to be accomplished due to the rarity of the disease.