MAMMARY MUCINOUS LESIONS - CONGENERS, PREVALENCE AND IMPORTANT PATHOLOGICAL ASSOCIATIONS

A retrospective histopathological study was undertaken to determine th e prevalence of mucin filled ducts and their associated mucinous proli feration in 962 breast cancers and 335 benign lesions. A total of 35 ( 3%) cases with mucin filled ducts was identified and 27 (2%) of these showed mucin extravasation into the adjacent stroma, changes character istic of mucocoele-like lesions. This constitutes the largest series r eported to date. Of the mucocoele-like lesions 12 were prototypic scre en-detected cases: 11 of which were mammographically detected on accou nt of suspicious microcalcification and eight cases (67%) exhibited mu cinous atypical ductal hyperplasia without overt malignancy. A further 12 mucocoele-like lesions were incidental Endings in screen-detected (11) and symptomatic (one) cancers, the majority of which were invasiv e ductal carcinomas of no special type. In six of these cases (50%), m ucinous atypical ductal hyperplasia or ductal carcinoma in situ was pr esent. Thirty mucinous carcinomas constituted 3% of all cancers and th ree cases had associated mucocoele-like lesions. Mucinous atypical duc tal hyperplasia or ductal carcinoma in situ was also associated with 1 1 cases of mucinous carcinoma. In six mucinous carcinomas, amorphous m icrocalcification with a Similar appearance to that of benign mucocoel e-like lesions was identified in the mucin, suggesting a possible link between the two lesions. Mucin-filled ducts or mucocoele-like lesions were almost twice as frequent in screen-detected as in symptomatic le sions. The presence of mucinous atypical ductal hyperplasia in screen- detected mucocoele-like lesions, a decade earlier than the peak of muc inous carcinoma, is a possible risk factor for subsequent invasive mal ignancy. Mucin-filled ducts, mucocoele-like lesions, mucinous atypical ductal hyperplasia or ductal carcinoma in situ and mucinous carcinoma may represent different stages of the same disease process. Our findi ngs suggest that patients with mucin-filled ducts of mucocoele-like le sions merit close follow-up.