Aims: To document the spectrum of lesions associated with mucin extravasation (ME) in breast core biopsy specimens, and to correlate with open surgical excisions.
Methods and results: Thirty-nine lesions in 37 women with ME on core biopsies constituted the study group. Fibrocystic change (FC), atypical ductal hyperplasia (ADH) and ductal carcinoma in situ (DCIS) were found in 21 (53.8%), 13 (33.3%) and four (10.3%) core biopsy specimens, respectively, with one (2.6%) consisting only of mucin pools. Except for the latter, all disclosed mucocoele-like lesions (MLL) accompanying ME. Columnar cell lesions (CCL) were frequently observed (84.6%). On open biopsy, three cases underdiagnosed on core biopsy included FC that later disclosed ADH; one ADH lesion on core later upgraded to DCIS; and a case of mucin pools that revealed mucinous carcinoma on excision. The extent of CCL on core biopsy appeared to predict sinister lesions on open excision. For calcified lesions that were completely removed on core biopsy, there were no malignant lesions discovered on open excision that had not already been diagnosed preoperatively.
Conclusions: ME and MLL on core biopsy warrant close radiological–pathological correlation. When the entire radiological abnormality has been removed with large core mammotome biopsy specimens, surgery may potentially be avoided in histologically benign lesions, although such an approach requires further validation.