Extensive intraductal carcinoma of the breast refers to a type of breast cancer in which ≥ 25% of ductal carcinoma in situ is present in invasive tumors and there is a scattered distribution of ductal carcinoma in situ (DCIS) in or around the invasive carcinoma. Compared with DCIS negative for extensive intraductal component, DCIS positive for extensive intraductal component is not sensitive to radiotherapy. Mckissock surgery was applied in breast-conserving surgery for breast cancer in 2016. Jianyi Li and the team members (Shengjing Hospital of China Medical University, Shenyang, China) applied this technique in breast-conserving surgery with preservation of the nipple-areola complex. This surgical technique is suitable for low-grade malignant tumors and has better prognosis than radical mastectomy. The purpose of this study is to investigate postoperative disease-free survival and quality of life after modified radical mastectomy versus expanded Mckissock surgery for extensive intraductal carcinoma of the breast. Results from this study will indicate the efficacy of expanded Mckissock surgery in the treatment of extensive intraducatal carcinoma of the breast.