Monarch Disease Ontology id MONDO_0006270 (lobular breast carcinoma in situ) is a non-invasive adenocarcinoma of the breast characterized by a proliferation of monomorphic cells completely filling the lumina. The overall lobular architecture is preserved. It is frequently multifocal (90% in some series) and bilateral. It seldom becomes invasive; however there is an increased risk of infiltrating ductal adenocarcinoma. Also known as: LCIS, lobular Ca in situ of breast, lobular Ca in situ of the breast, lobular carcinoma in situ, lobular carcinoma in situ (LCIS), lobular carcinoma in situ of breast, lobular carcinoma in situ of the breast, lobular carcinoma in situ of the breast (LCIS).