BACKGROUND: Metaplastic breast carcinoma is a rare entity characterized by rapid growth and heterogeneous histological features. It comprises less than 1% of all breast cancers, and no definitive treatment has yet been identified.

CASE REPORT: We describe here a patient who presented with acute hypercalcemia and was found to have a large ulcerated breast mass. Once the patient’s hypercalcemia was stabilized, she underwent complete surgical resection that revealed a large, cavitary, necrotic mass measuring over 11 cm. The final surgical pathology revealed metaplastic carcinoma with extensive squamous differentiation and ductal carcinoma in situ. At the request of her family, no additional treatment was pursued.

CONCLUSIONS: While there is not a significant body of data on the pathogenesis of metaplastic breast carcinoma, it is typically hormone receptor negative and has a variable response to chemotherapy. Surgical excision is the most commonly pursued treatment.

Keywords: Breast, Carcinoma, Squamous Cell, Metaplasia, Breast Neoplasms, Hypercalcemia