Context.—: Mucinous lesions of the breast encompass many entities ranging from benign to malignant and nonneoplastic to neoplastic. Lesions discussed under this category are mucocele-like lesion, mucinous carcinoma, mucinous micropapillary carcinoma, solid papillary carcinoma, mucinous cystadenocarcinoma, mucoepidermoid carcinoma, invasive lobular carcinoma with extracellular mucin, mucinous ductal carcinoma in situ, and metastasis.
Objective.—: To review clinical, pathologic, and molecular features of mucinous lesions of the breast, their differential diagnoses, and challenging features on core needle biopsies.
Data sources.—: The existing scientific and clinical literature as of December 2021.
Conclusions.—: The category of mucinous lesions of the breast is vast and the differential diagnosis can be challenging, especially on core needle biopsies. In all cases, clinical, radiologic, and pathologic correlation is necessary to reach a comprehensive diagnosis. Given that the prognosis and management of each entity is different, being aware of these entities and their nuances is critical for a pathologist to guide accurate management.
© 2023 College of American Pathologists.