Clinical Management of Mucocele-Like Lesions of the Breast with Limited or no Epithelial Atypia on Core Biopsy: Experience from Two Institutions

Purpose: Mucocele-like lesions of the breast identified on core biopsy are rare high-risk lesions associated with variable upgrade rates to carcinoma on excision. We aimed to identify the clinicoradiopathological features that can help optimize management of this lesion. Methods: We evaluated 50 mucocele-like lesions identified on core biopsies from two institutions, including 36 with no atypia and 14 with limited atypia. Outcome data from excision or clinicoradiological follow-up were reviewed with core biopsy results. Results: Radiological targets were calcifications in 74% of cases, calcifications with associated mass or density in 16%, and mass in 10%. One of the 16 excised lesions without atypia on core biopsy, which was a mass lesion, was upgraded to mucinous carcinoma on excision. Of the 12 excised lesions with limited atypia, none were upgraded on excision. Among the lesions not excised, 20 without atypia had a median follow-up of 61 months, and 2 with limited atypia had follow-up of 97 and 109 months. None of these 22 patients had new development of their lesions on follow-up. The upgrade rate was 2% in our entire cohort, 3% for lesions without atypia, and 0% for lesions with limited atypia. Conclusions: Clinicoradiological surveillance can be appropriate when a mucocele-like lesion without atypia is identified on core biopsy for a non-mass lesion with pathological-radiological concordance. For mucocele-like lesions with limited atypia, a nonsurgical approach could be considered if the atypia by itself does not warrant excision. The latter recommendation requires careful clinicopathological correlation and support from additional studies.