Recently, the number of radial scars (RS)/complex sclerosing lesions (CSL) of the breast has been increasingly detected by mammography screening. Six RS/CSL cases encountered clinicopathologically in the last 2 years are presented. All patients were pre-menopausal. Three cases were detected by ultrasonography (US) screening, and the others were detected by mammography (MG) screening. Partial mastectomy was carried out for both diagnosis and treatment, since it was difficult to discriminate whether RS/CSL accompanied breast cancer even by US, MG, MRI, aspiration cytology, and spring-loaded core needle biopsy (CNB). RS/CSL was histologically confirmed in all cases, and atypical ductal hyperplasia (ADH) or ductal carcinoma in situ (DCIS) accompanied RS/CSL in each case. At present, the clinical diagnosis of complicated breast cancer is difficult. Therefore, we selected partial mastectomy that resects a wider area than surgical biopsy to adequately diagnose breast cancer and to achieve a resected margin that is free from breast cancer. But it may be that partial resection should be performed in case of older age with larger RS/CSL, since it is over-surgery for RS/CSL without breast cancer. Further studies where complicated breast cancer is certainly identified are necessary.