A Case of Metaplastic Breast Cancer with Prolonged Response to Single Agent Liposomal Doxorubicin.

Female breast cancer accounts for 14% of all new cancer cases in the United States. Metaplastic breast carcinomas (MpBC) are less than 1% of all mammary tumors. Limited clinical information exists on the prognosis and treatments for MpBC due to its rarity and the histological diversity of the tumor cells. We report a case of metastatic MpBC with osseous differentiation who had a marked response to liposomal doxorubicin. This 54-year-old female presented with a 2.5 x 2.6 cm oval-shaped irregularly marginated density in the outer lower quadrant of the left breast, cT2N0M0. Biopsy revealed an invasive metaplastic carcinoma, triple negative, with osseous and focal chondroid differentiation. Genetic testing showed a mutation in the BRCA1 gene. Approximately seven months after a left mastectomy, the patient presented with biopsy-proven metastatic disease and was initiated on therapy with a single agent, liposomal doxorubicin, 50 mg/m(2) every 28 days. The patient achieved maximum response after cycle three and continued to have stable disease for 18 months (20 cycles). Based on the pathologic phenotype, we would have predicted that she would have had a poor and short response to anthracycline. This case illustrates an increased sensitivity of BRCA1-mutated cancers to anthracycline therapies, irrespective of pathologic classification.