Metaplastic carcinoma of breast with heterologous mesenchymal differentiation (carcinosarcoma) having an endothelial component: a case report.

Background: Metaplastic breast cancer with heterologous mesenchymal differentiation, known earlier as carcinosarcoma, consists of both infiltrating ductal carcinoma cells and mesenchymal cells, and is associated with an aggressive course. The mesenchymal component is rarely endothelial, with only two previously reported cases. The present case is the third among those. Moreover, the disease outcome was good, unlike the usual course of carcinosarcoma.

Case presentation: A 59-year-old multiparous woman of Indo-aryan ethnicity developed a lump in her left breast and was diagnosed with breast carcinosarcoma having an endothelial component, with the help of histopathological examination and immunohistochemistry. The tumor was surgically removed; then the patient received adjuvant chemotherapy, epirubicin, and cyclophosphamide, followed by adjuvant radiotherapy to the whole breast, followed by tumor bed boost. The patient was clinic-radiologically disease-free even at 26 months post-treatment.

Conclusion: Surgery followed by adjuvant chemotherapy and radiotherapy gives better outcomes compared with surgery alone, with a doubtful role of neoadjuvant chemotherapy. Targeted therapies can be considered in patients not responding to conventional treatment.