Pathologic Spectrum of Secretory and Mucinous Breast Lesions

Abstract

Context.—The morphologic spectrum of secretory breast lesions encompasses benign, borderline, and malignant lesions. They are characterized by luminal pink, proteinaceous secretions and variable degrees of cytologic atypia ranging from low grade to high grade, with frequent papillary formations. Other lesions, benign and malignant, can also show luminal and extraluminal secretions and share similar features with secretory lesions, making them diagnostically challenging. Objective.—To discuss the differential diagnosis of secretory breast lesions, emphasizing the most important diagnostic features of benign and malignant lesions. Lesions with intraluminal secretions discussed at length in this review include pregnancy-like hyperplasia, cystic hypersecretory hyperplasia, collagenous spherulosis, microglandular adenosis, hypersecretory carcinoma, and secretory carcinoma. Lesions with extravasated mucin, such as mucocele-like lesions and mucinous carcinoma, are also briefly discussed. Data Sources.—Published articles obtained from a PubMed search of the English literature were the primary source for this review. Conclusions.—Lesions with secretory features described in this review show a pathologic spectrum, sometimes even within the same lesion. As a consequence, one should employ a low threshold for recommending reexcision on a core biopsy containing benign-appearing hypersecretory glands and use all ancillary data, including clinical presentation, imaging findings, morphology, immunohistochemistry, and molecular pathology, to render a final diagnosis.