Image Description
Microscopically, the borders of medullary carcinoma are smooth, rounded, and of "pushing type" (left panel). The border tends to push aside the breast parenchyma and fat rather than infiltrating it. Non-neoplastic glands and fat are therefore not seen within the main body of the tumor. In contrast, the right panel shows the borders of an infiltrating ductal carcinoma with medullary features. The tumor borders freely infiltrate into the surrounding fat. The pattern shown in the right panel is not compatible with a diagnosis of medullary carcinoma.
About the Disease
Medullary carcinomas make up less than 5% of all breast carcinomas. They share a number of features with BRCA-1 associated breast cancers, including - relatively young age at diagnosis, lympho-plasmacytic infiltrate, high-grade morphology, triple-negative phenotype, and p53 mutations. Among breast cancers arising in BRCA-1 carriers, about 13% are medullary carcinomas. They are bulky, soft, and well-circumscribed with pushing borders that dont infiltrate into the surrounding breast tissue or fat. They show diffuse growth pattern with high-grade nuclei, frequent mitoses and abundant eosinophilic cytoplasm with a syncytial appearance. There is a prominent lymphoplasmacytic infiltrate within and around the tumor composed of peripheral T-cells (with numerous activated cytotoxic lymphocytes) and IgA-producing plasma cells. It is believed to be host reaction to the tumor and is thought to play a role in better prognosis seen with this tumor as compared to other breast cancers. The 10-yr survival rate is about 84%. The immunohistochemical profile of medullary carcinoma is similar to conventional invasive ductal carcinonma. They are usually positive for CK7, S-100 protein, and P53. Cytokeratin 20 is generally negative. ER, PR, and HER2 are negative (triple negative phenotype).