Medullary carcinoma of the breast is one of the pathological types of breast, which generally has the following characteristics: 1) clear boundary, sometimes difficult to be distinguished from fibroma; 2) lack of glandular duct-like structure; 3) frequent infiltration of lymphocytes in the paracancerous tissues of the breast; and 4) large differences in the heterogeneity of the nuclei of the tumor. This is a typical medullary carcinoma of the breast. However, most of them are atypical medullary carcinoma of the breast, which may or may not be accompanied by lymphocytic infiltration. Most of the clinical manifestations of medullary carcinoma of the breast are mainly confined lumps, and calcification is seldom seen in molybdenum imaging, and it is an isolated lump with relatively clear boundaries.