The aim of the current study was to identify a select group of patients with mild atypia who do not need surgical excision after large-core needle biopsy (LCNB) of the breast.Nineteen (70%) of 27 patients with ductal atypia found on LCNB had subsequent surgical excision. These 19 patients were retrospectively assigned to 3 groups according to the severity of the atypia found, which was compared with the final pathologic specimen after surgical biopsy.Cancer was identified through surgical biopsy in 6 (32%) of 19 patients. The severity of atypia seen on the LCNB specimen strongly correlated with subsequent cancer identification (P<.01). Two (33%) of 6 patients in group 2 (true atypical ductal hyperplasia [ADH]) and 4 (80%) of 5 patients in group 3 (severe ADH, borderline ductal carcinoma in situ) had cancer after surgical biopsy. No cancer was found after surgical biopsy in 8 patients in group 1 (mild atypia, not meeting criteria for ADH).The results of this study suggest that surgical excision can be avoided after LCNB of the breast in patients with only mildly atypical lesions that do not meet criteria for ADH. Patients with true ADH should continue to have surgical excision.