Abstract: Objective: To evaluate the value of dissecting level Ⅲ lymph nodes in modified radical mastectomy of breast cancer patient with positive axillary lymph nodes.Methods: The breast carcinoma patients with positive axillary lymph nodes were screened by physical examination or ultrasound imaging.The patients were treated with the modified radical mastectomy or modified radical mastectomy combined with level Ⅲ lymph nodes dissection.The clinical effects of two kinds of operations were compared.Results: Forty-two patients were treated with level Ⅲ lymph nodes dissection.Among 42 patients,the positive axillary lymph nodes in 41 cases(accompanied by postive level Ⅲ lymph nodes in 13 cases) were found.The rates of 3-year distant metastasis and supraclavicular lymph node metastasis were 9.5% and 2.4%,respectively.Seventeen patients were treated with the modified radical mastectomy,the rates of 3-year distant metastasis and supraclavicular lymph node metastasis were 35.3% and 23.5%,respectively.The differences of the rates of 3-year distant metastasis and supraclavicular lymph node metastasis between two kinds of operations were statistically significant(P<0.05).The overall survival rates of the patients treated with the modified radical mastectomy and modified radical mastectomy combined with level Ⅲ lymph nodes dissection were 92.9% and 88.2%,respectively,the difference of which was not statistically significant(P>0.05).Conclusions: Dissecting level Ⅲ lymph nodes in the treatment of the patients with positive axillary lymph nodes can thoroughly clean the axillary lymph nodes,and improve the postoperative treatment and prognosis.