Carcinosarcoma of the Breast Presenting As a Gyant Cystic Lesion

INTRODUCTION: Carcinosarcoma of the breast is a rare entity and has a worse outcome than ductal and lobular carcinoma. It is a biphasic lesion with a mesenchymal and epithelial component. CASE REPORT: a 57 years old female patient was first seen at Program of Mastology presenting with an enlarged, red and painful left breast, with evolution of six months. At the physical exam the left breast was about three times the size of the right breast, had a cystic consistency and showed inflammatory signs. She denied fever during that period. Her sister was diagnosed with breast cancer. She underwent a breast drainage that revealed a cyst with approximately 1, 000 ml of sero- hematic fluid and a hard and irregular mass surrounding it. Biopsy was performed and pathology exam revealed a carcinosarcoma expressing S100, Vimentin and Estrogen receptor. Clinical and radiological staging showed no signs of metastasis. Soon after the biopsy, on the site an exofitic lesion with a necrotic area appeared concomitantly with two coalescent lymph nodes in the left axilla. She underwent a mastectomy with axillary clearance. The histological exam confirmed the carcinosarcoma sized 10.5, infiltrating the skin and clear margins. One out of 11 lymph nodes removed was infiltrated by cancer cells. The patient is well and will go through adjuvant chemotherapy. DISCUSSION: Carcinosarcoma of the breast is a very aggressive lesion and is a diagnostic and therapeutic challenge. In the case presented the patient had an enormous cystic lesion that could be mistaken with mastitis. Biopsy with a representative amount of the lesion was fundamental and the immunohistochemistry confirmed the diagnosis. This entity needs to be treated aggressively due to its poor prognosis.