Papillary Neoplasms of the Breast: Histopathologic Di-versity, Molecular Profile, and Clinical Implications— A Review with a Five-Case Series

Abstract

Papillary carcinoma of the breast rep- resents an uncommon and morphologically diverse category of breast malignancies, com- prising roughly 0.5% of newly diagnosed cases worldwide. These tumors occur most frequently in postmenopausal women and demonstrate a comparatively higher relative incidence in male patients than many other forms of breast carci- noma. Papillary carcinoma encompasses mul- tiple distinct entities, including papillary ductal carcinoma in situ (DCIS), encapsulated papil- lary carcinoma (EPC), solid papillary carcinoma (SPC), and invasive papillary carcinoma (IPC). Despite shared papillary architecture character- ized by fibrovascular cores lined by neoplastic epithelial cells, these subtypes differ signifi- cantly in biological behavior, prognosis, and management. Immunohistochemistry plays a central role in diagnosis, particularly in assess- ing myoepithelial cell presence to distinguish benign from malignant lesions. Molecular stud- ies demonstrate that most papillary carcinomas exhibit a luminal phenotype and frequently har- bor PIK3CA mutations, with genomic profiles overlapping those of estrogen receptor–positive invasive ductal carcinoma. Clinical outcomes are generally favorable, particularly for EPC and SPC although diagnostic and therapeutic controversies persist. This review synthesizes current knowledge regarding classification, his- topathology, molecular characteristics, imaging features, management strategies, and prognos- tic outcomes.