PURPOSE: Intraductal papilloma (IDP) is a benign breast disease with malignant potential, for which complete surgical excision is usually recommended. The aim of the present study was to investigate predictive factors for upgrading patients with a benign papillary lesion (BPL). METHODS: This study was an observational study using a prospectively collected cohort. In total, 13,049 patients who underwent a core needle biopsy (CNB) for a breast lesion between January 2009 and May 2015 were enrolled. We reviewed all patients with pathologically confirmed BPL from a CNB. RESULTS: Surgical treatment was performed for 363 out of a total of 592 lesions. According to the pathological differences, the lowest upgrade rate was shown in IDP without atypia (without atypia, 6.0%; with atypia, 26.8%; papillary neoplasm, 31.5%; p<0.001). The univariate analysis showed that, in IDP without atypia, the age at diagnosis, size of BPL on ultrasonography, and density on mammography were associated with upgrading. The multivariate analysis revealed that age >54 years and lesion size >1 cm were significantly associated with upgrade to malignancy (odds ratio [OR]=4.351, p=0.005 and OR=4.236, p=0.001, respectively). CONCLUSION: The indications for surgical treatment can be defined as age >54 years and mass size >1 cm, even in IDP without atypia in the CNB results; this also includes cases of IDP with atypia or papillary neoplasm. Therefore, we suggest that close observation without surgery is sufficient for younger women with a small IDP without atypia.