Mucocele-like lesions (MLL) of the breast are characterized by cystic architecture with stromal mucin and frequent atypia, but it is unknown whether they convey long term breast cancer risk. We evaluated 102MLL that were derived from a single institution benign breast disease (BBD) cohort of 13412 women who underwent biopsy from 1967–2001.MLL were histologically characterized by type of lining epithelium, architecture of the lesion, associated atypical hyperplasia (AH) and for incidence of breast cancer (14.8 years median follow-up). A relatively large proportion of MLL (42%) were diagnosed in women >55 years of age AH was significantly more frequent in MML patient compared to the cohort overall (27% vs 5%, p<0.001). Breast cancer has developed in 13 patients with MLL.. This frequency is only slightly higher than population expected rates overall (Standardized incidence ratio (SIR) 2.28, 95% CI 1.21–3.91), and not significantly different from women in the cohort with (non atypical) proliferative breast lesions. Younger women (<45) with MLL had a non-significant increase in risk of cancer compared to the general population (SIR 5.16, 95% CI 1.41–13.23). We conclude MLL is an uncommon breast lesion that is often associated with co-existing AH. However, in women over age 45, MLL do not convey additional risk of breast cancer beyond that associated with the presence of proliferative disease.