Although ductal carcinoma in situ(DCIS)is generally cured by surgical resection, it has been suggested that resection is over-treatment for some patients with DCIS. The aim of this study was to reconsider operative indications for patients with DCIS by examining clinicopathological features of 23 patients who underwent surgical resection for DCIS in our institute over a single year. Postoperative histological examination revealed that there were Luminal and HER2-positive subtypes, but no triple negative cancers. We found coincidental invasive ductal carcinoma(IDC)in 5 patients, and in all 5 the tumor size exceeded 60 mm. There was no coincidence of IDC in patients with a Ki-67 index ≤5%. Positive surgical margins were observed in 7 patients, all of which were histologically diagnosed as DCIS. Only 1 of the 7 patients underwent additional surgical resection; the 6 remaining patients, including 2 patients who received no treatment, did not undergo additional resection. All patients including those with positive surgical margins have had a 5-year relapse-free survival. Our findings imply that the subgroup of DCIS patients without IDC could be followed up without surgery.