Objective:Axil ary lymph node status is one of the most important prognostic indicator of survival for breast cancer, especial y in ductal carcinoma in situ (DCIS). The purpose of this study was to investigate whether sentinel lymph node biopsy (SLNB) should be performed in patients with an initial diagnosis of DCIS. Methods:A retrospective study was performed of 124 patients with an initial diagnosis of DCIS between March 2000 and June 2014. The patients were treated with either SLNB or axil ary node dissection during the surgery, and we compared the clinicopathologic characteristics, image features, and immunohistochemical results. Results:Eighty-two patients (66.1%) had pure DCIS and 25 (20.2%) had DCIS with microinvasion (DCISM), 17 (13.7%) updated to invasive breast cancer (IBC). 115 patients (92.7%) underwent SLNB, among them, 70 patients (56.5%) underwent axil ary node dissection. 3 of 115 patients (2.6%) had a positive sentinel lymph node, only 1 (1.4%) of 70 patients had axil ary lymph node metastasis, in 84 patients (66.7%) who were diagnosed DCIS by core needle biopsy (CNB) and vacuum-assisted biopsy (VAB). 26 patients (31.0%) were upstaged into IBC or DCISM in the final histological diagnosis. The statistical y significant factors predictive of underestimation were large tumor size, microcalci-fications, comedo necrosis, positive Her-2 status, negative estrogen receptor status. Conclusion:The metastasis of sentinel lymph nodes in pure DCIS is very low, but the underestimation of invasive carcinoma in patients with an initial diagnosis of DCIS is an usual incident, especial y in the cases when DCIS is diagnosed by CNB or VAB. Our findings suggest patients presenting with a preoperative diagnosis of DCIS associated with large tumor sizes, microcalcifications, comedo necrosis, positive Her-2 status, negative ER status are more likely to be DCISM and IBC in final diagnosis. SLNB should be performed in this part of patients.