Purpose To explore the expressional differences of immunohistochemical indicators between the non-mass-like and mass-like breast cancers,and to identify the biological characteristics of non-mass-like breast cancer.Material and Methods Various immunohistochemical indicators (HER2,ER,PR,Ki-67) were analyzed in 19 cases non-mass-like cancer and 18 cases mass-like breast cancer retrospectively,and the expressional differences of the two groups were compared.Results 12 cases (63.2％) were diagnosed DCIS in the non-mass-like breast cancer group,but in the mass-like breast cancer group,the majority (12 cases,66.7％) were invasive cancer.HER2,ER,PR expression had no statistical difference between the two types (P＞0.05).But the Ki-67 positive rate expressed in non-mass-like breast cancer was lower significantly (P＜0.05).Conclusion The HE immunohistochemical characteristics of non-mass-like breast cancer are overlapped with that of mass-like breast cancer,but Ki-67 expression has significant difference between the two groups.There are some differences in biological characteristics of these two kinds of breast cancers.