Pathology of breast papillary neoplasms: Community hospital experience

In this study, 550 breast papillary neoplasms collected in a community hospital over more than ten years were reviewed and analyzed. This included 457 intraductal papillomas, 53 papillary carcinomas, 35 papillary DCIS and five invasive papillary carcinomas. The diagnostic rate of papillary neoplasms increased over time, likely due to better recognition by pathologists. Intraductal papillomas occurred most frequently in the upper outer quadrants and contained ADH/DCIS in 19% of cases. A total of 28% of non-incidental papillomas were associated with ADH/DCIS, and 29% of patients with papillomas had ADH/DCIS in adjacent tissue; nearly half of papillomas that were > 1 cm in size contained ADH/DCIS in the papilloma or adjacent to it. No single feature could predict an upgrade on excision for non-atypical intraductal papillomas diagnosed on core biopsy. There was no significant difference in the association of ADH/DCIS with central or peripheral papillomas. The overall upgrade rate of non-atypical intraductal papillomas to DCIS on excision was 2%, which justifies the conservative management of non-atypical sub-centimeter lesions. Papillary carcinomas occurred in older than intraductal papilloma patients and were most frequent in the upper quadrants. Although classically devoid of a myoepithelial cell layer, papillary carcinomas may contain some residual or even an ample myoepithelial cell layer in the papillae. An association between papillary carcinoma and conventional invasive carcinoma was found in 40% of EPCs and 89% of SPCs. Papillary DCIS was usually low- or intermediate-grade. The presence of a myoepithelial cell layer in the papillae was not inconsistent with this diagnosis. Invasive papillary carcinoma may have two histologic patterns: papillary and cribriform.