Carcinosarcoma of Breast with Hormone Receptor and Her2/neu Positivity

Carcinosarcoma is an extremely rare tumor of the breast comprising of two distinct cell lines i.e. the epithelial and mesenchymal. It is a highly aggressive tumor with a poor prognosis compared to other breast cancers with a reported incidence of less than 1% of all the breast cancers. A 35 year old female presented to surgical outpatient with a fungating mass in the right breast where cytological analysis from the affected areas revealed spindle cells of malignant potential. A modified radical mastectomy was performed and following histopathological examination of the excised tissue, a final diagnosis of carcinosarcoma of breast was concluded. Immunological staining done showed a negative staining for PR and positive staining for ER, Her-2/neu and CK receptors, as against the conventional triple negative staining pattern. Along with a rare staining pattern of this rare tumor reported in literature, this case merits presentation owing to its diagnostic and therapeutic challenges.