Medullary carcinoma is a poorly differentiated breast cancer tumor with a high histologic grade and a paradoxically good prognosis. It accounts for only 5% of all breast cancers (1–3). Thus far, only histologic criteria are used to define this tumor type; no genetic characteristics have been identified. An alteration in the p53 gene (also known as TP53) is found in 20%–40% of invasive breast cancers, but its status in medullary breast cancer is poorly documented. Immunochemical detection of a stable mutant p53 in nuclei of tumor cells is the most convenient assay, but the correlation of the results from such an assay with results from molecular analysis, such as sequencing, is not totally in agreement (4). The frequency of p53 mutations in breast cancer is around 20%, but immunohistochemical analysis detects p53 accumulation in 30%–40% of tumors