Adenosis, Sclerosing Lesions, Microglandular Adenosis, and Mucocele-Like Lesions

Abstract

Sclerosing adenosis, sclerosing lesions, microglandular adenosis, and mucocele-like lesions are benign lesions that may mimic invasive carcinoma on routine histology. Adenosis and sclerosing lesions are small glandular proliferations that may resemble well-differentiated invasive ductal or tubular carcinoma, whereas mucocele-like lesions may be confused with mucinous carcinoma. It may be especially difficult to recognize these lesions in the limited core needle biopsy sample, and therefore, it is important to maintain a low threshold for diagnostic work-up. Immunohistochemical studies for myoepithelial cell markers facilitate the correct diagnosis in challenging cases. However, a notable exception, microglandular adenosis, lacks myoepithelial cells, and must be distinguished from well-differentiated invasive carcinoma by its S-100 protein immunoreactivity and triple negative phenotype.