DCIS and LCIS are confusing and outdated terms. They should be abandoned in favor of ductal intraepithelial neoplasia (DIN) and lobular intraepithelial neoplasia (LIN).

The terms ductal and lobular intraepithelial neoplasia (DIN and LIN) were introduced by Tavossoli 15 years ago, who proposed they should replace, respectively, ductal and lobular carcinoma in situ (DCIS and LCIS). This proposal has been slowly gaining ground. We argue that DCIS and LCIS should now be definitively abandoned. Bringing together 'in situ' and other entities into the simpler and more logical DIN/LIN framework--as has been done with intraepithelial neoplasias of cervix, vagina, vulva, prostate, and pancreas--would eliminate the artificial and illogical distinctions between 'not cancers' (e.g. flat epithelial atypia, atypical ductal hyperplasia--now classified as low grade DIN) and 'cancers' (e.g. DCIS--now considered medium-high grade DIN). Elimination of the term 'carcinoma' from entities that cannot metastasize will reduce confusion among health professionals and patients, and contribute to reducing the risk of overtreatment, as well as reducing adverse psychological reactions in patients.