Carcinosarcoma of the breast, also known as metaplastic carcinoma, is a rare entity with few cases reported in the literature. A 43-year old female patient presented with a mass in her left breast for which she got operated by a local surgeon 6 months back. Physical examination was done when she presented with a large lump at the site of previous surgery and revealed a diffuse breast lump measuring about 15x10 cm. Ultrasonographic findings showed well delineated mass densities and focal areas of microcalcifications. Radical mastectomy was performed keeping in view the large size of the tumor. Histopathological examination revealed carcinosarcoma of the breast. Histologic grade of the tumour was III. Tumor cells were positive for Vimentin in the sarcomatous areas, pancytokeratin and EMA in carcinomatous areas, and negative for estrogen and progesterone receptors. There was no metastasis to axillary lymph nodes or distant metastasis. Along with a review of the literature, we present the information regarding the clinical and histological findings of the patient presenting as carcinosarcoma.