Objective To investigate the clinical features and bilogical characteristics of the medullary carcinoma of the breast. Methods 27 cases of typical medullary carcinoma and 34 cases of atypical medullary carcinoma were analyzed. Results The results showed that the incidence of medullary carcinoma of breast was 6.6% of the total breast cancers, and the 3-,5- year survived rates were 96.29%,88.88% in the typical medullary carcinoma; 91.17%,79.41% in the atypical medullary carcinoma.Conclusion The common features of medullary carcinoma were fairly clear boundary mass.This suggest that medullary carcinoma should be made a definite diagnosis by needle and freeze biopsy.