Objective:To analyze the risk factors of delayed breast cellulitis (DBC) after breast conserving surgery in breast cancer. Methods:The clinical data of 152 patients received breast conserving surgery during January 2001 to December 2006 in Breast Disease Center of Peking University First Hospital were analyzed retrospectively.All the patients were identified by the accepted criteria: diffuse breast erythema,edema,tenderness,and warmth occurring >3 months after definitive surgery and >3 weeks after radiotherapy.Forteen patients were diagnosed DBC. Results:The incidence of DBC in the group was 9.2% (14/152). The median time to onset of DBC was 6.2 months after breast conserving surgery.Primary tumor T stage, upper outer quadrant tumor,>15 axillary lymph nodes removed and the breast hematoma/seroma after surgery,were significantly associated with DBC.Age,diabetes,neoadjuvant chemotherapy, positive axillary lymph nodes metastasis were not the factors associated with DBC. Conclusion:Lymphatic drainage damaged by surgery procedures and radiotherapy maybe the most important factors contributed to the onset of DBC.