Abstract: Objective: To investigate the characteristics, diagnosis and treatment of occult breast cancer. Methods: Data of 68 cases with occult breast cancer were analyzed retrospectively. Results: All patients of the group received biopsy and immunohistochemical M₄G₃-test, among which radical or modified mastectomy was conducted in 65 cases and axillary node excision in 3. Postoperative chemotherapy and radiotherapy were carried out in all patients. The 5 and 10-year disease-free survival rate was 77.9% and 58.12% respectively. The detection rate of primary focus was 33.8% (22/65). With the help of subserial section of total breast, the overall detection rate was up to 86.2% (56/65). Conclusion: The occult breast cancer should be taken into consideration in case presented axillary mass with exclusion of the metastasis from other sites. The histological diagnosis such as axillary nodes biopsy and immunohistochemical M₄G₃-test are the mainstay for final diagnosis of the occult breast cancer. The subserial section examination of total breast is needed for improving the detection rate of primary focus. Radical or modified radical mastectomy with adjuvant radiotherapy, chemotherapy and endocrinological therapy is the treatment of choice for occult breast cancer.