Introduction: Few data have been reported that address the biologic features of medullary breast carcinoma (MBC) in the context of their clinical outcome.We sought to compare the baseline demographics, standard pathologic factors and long term clinical outcomes between MBC and infiltrating ductal carcinoma-not otherwise specified (IDC-NOS) using a large database.Methods A total of 2 490 individual patients meeting inclusion criteria were identified from 1999 to 2010:2 202 with pure infiltrating ductal and 188 with typical medullary breast carcinomas.The clinical and biological features, the overall survival (OS) and recurrence/ metastasis-free survival (RFS) were compared for both groups.Results In comparison with IDC-NOS, a higher fraction of MBC occurred among the subgroup of young patients defined as age 40 years or younger in our cohort.Despite its relatively earlier onset age at diagnosis, these cases of MBC evidenced less aggressive tumor features such as lower tumor stage, smaller tumor size and lower proportion of nodal involvement than IDC-NOS, but immunohistochemical staining demonstrated MBC more often appealed to be triple negative phenotype.Although the clinical behavior of MBC was not commensurate to its pathologic features, women diagnosed with MBC had a lower frequency of experiencing recurrence/metastasis (P=0.032) and death (P=0.042) as those with IDC-NOS, and the 10-year OS and RFS was significantly higher for MBC (91% and 74%) compared to IDC-NOS (81% and 64%).Moreover, the univariate beneficial prognostic effects of MBC phenotype had appeared to be restricted to those cases with lager tumor size (≥2 cm), and the majority of whom received adjuvant chemotherapy or not received hormone therapy.Multivariate analysis revealed TNM stage were statistically significant factors for survival.Conclusion MBC in Chinese women showed less aggressive behavior and better prognosis than IDCNOS, and this favorable outcome was maintained after 10 years.TNM stage appeared to be the most significant predictor of worse prognosis.As for the choice of surgical procedure, breast conserving therapy should be preferred to mastectomy in the treatment with early stage MBC.