Benign mucocele-like lesions of the breast: revisited.

Mucocele-like lesions of the breast are ruptured ducts that discharge their contents into the stroma. They constitute a spectrum from benign to atypical to malignant. The current management of these lesions diagnosed on core biopsy is excision. The goal of our study was to evaluate the necessity of this practice for benign mucocele-like lesions. Retrospective review of the pathology database from 1 January 2000 to 1 June 2008 identified 61 cases, with follow-up information available in 50 cases. Clinical, radiological, and pathological information was correlated. Core biopsies were reviewed to confirm the diagnosis and verify previous biopsy site. In all, 45 patients underwent surgery, whereas 5 patients were followed for >1 year and remained stable. Patient's ages ranged from 44 to 76 years. Most benign mucoceles were diagnosed stereotactically while targeting calcifications (93.3%); rarely, the lesion was a sonographically detected mass. Most excisions had no residual mucocele (37/45=82%). In seven cases (15.6%), atypical duct hyperplasia was present, three with residual mucocele. In one case, the residual mucocele showed a continuum from florid to atypical duct hyperplasia at the core biopsy site. The other six cases showed atypical duct hyperplasia adjacent to but not directly at the core biopsy site. The sizes of the benign mucoceles ranged from incipient to 0.6 cm, all containing calcifications except one, which was incidental. Radiological-pathological correlation was concordant in all cases except one with suspicious calcification, which was ductal carcinoma in situ on excision. In this series, the largest of its kind, the upstage rate of benign mucoceles diagnosed on core biopsy was 17.8%. With the exception of the ductal carcinoma in situ case, no radiological or morphological features were predictive of atypia. Thus, because of associated atypical duct hyperplasia, sampling reasons, and intralesional heterogeneity, we continue to recommend excision of benign mucocele-like lesions diagnosed on core biopsy.