Intraductal papillomas on core biopsy can be upgraded to malignancy on subsequent excisional biopsy regardless of the presence of atypical features.

Intraductal papillary lesions of the breast constitute a heterogeneous entity, including benign intraductal papilloma (IDP) with or without atypia and malignant papillary carcinoma. Differentiating between these diagnoses can be challenging. We re-evaluated core biopsy specimens that were diagnosed as IDP and the corresponding surgical excision specimens, and assessed the potential risk for the diagnosis to be modified to malignancy based on excision. By sorting the pathology database of the National Cancer Center Hospital, Tokyo, we identified 146 core biopsy cases that were histologically diagnosed as IDP between 1997 and 2013. The re-evaluated diagnosis was IDP without atypia in 79 (54%) patients, IDP with atypia in 66 (45%), and ductal carcinoma in situ (DCIS) in 1 (1%). Among the 34 patients (23%) who underwent surgical excision subsequent to core biopsy, histological diagnosis was upgraded to carcinoma, excluding lobular carcinoma in situ (LCIS), in 14 (41%) cases, including 4 (33%) of 12 IDPs without atypia and 10 (45%) of 22 IDPs with atypia. Complete surgical excision should be kept in mind for all IDPs diagnosed on core biopsy, not only IDPs with atypia but IDPs without atypia, especially when clinical or imaging diagnosis findings cannot rule out the possibility of malignancy, because papillary lesions comprise a variety of morphological appearances.