[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Breast](https://durgical.com/en/general-pathology/areas/breast/) › Lobular carcinoma in situ # Lobular carcinoma in situ - Lesion LCIS is an invisible, often bilateral change in the lobules found by chance; it marks a high risk of cancer in both breasts. Updated Nov 12, 2026 ## Key points - Cells: small, uniform, round nuclei, scant cytoplasm, intracytoplasmic mucin vacuoles (signet-ring cells); loosely cohesive. - E-cadherin loss (CDH1 inactivation) is the defining molecular change shared with invasive lobular carcinoma. - Usually incidental: no calcification, no mass; multicentric and often bilateral. - Risk of invasive cancer is raised in both breasts, of lobular and of ductal type. - Pleomorphic LCIS: larger pleomorphic nuclei, central necrosis and calcification; managed by excision like DCIS. ## What it is Lobular carcinoma in situ is a clonal proliferation of small, discohesive cells that fill and expand the acini of lobules. The cells have lost E-cadherin, the adhesion protein encoded by CDH1. Classic LCIS does not form a mass or calcifications, so it is found incidentally in biopsies taken for something else; it is often multicentric and bilateral. It is both a risk marker and a non-obligate precursor, raising the risk of invasive carcinoma in either breast. Pleomorphic LCIS, with large atypical nuclei and necrosis, behaves more like DCIS. ## Structure - Acini of a lobule expanded and filled with monotonous discohesive cells; the lobular outline is preserved. - Cells may spread along ducts beneath the luminal epithelium (pagetoid spread). - Myoepithelial cells remain around the expanded acini. ## Step by step - A luminal cell inactivates CDH1 by mutation and loss of the other allele. - Without E-cadherin, cells lose adhesion and proliferate as discohesive sheets within lobules. - The change arises in several lobules and both breasts, reflecting a field of risk. - Some clones invade and form invasive lobular carcinoma that grows in single files. ## Markers - E-cadherin negative - p120 catenin cytoplasmic - ER positive - HER2 negative (classic type) ## Clinical notes - Found incidentally; classic LCIS is managed by surveillance and risk-reducing options rather than wide excision. - Patients are offered closer imaging and may receive endocrine risk-reducing therapy. ## Memory aid Lobular cells let go of each other (no E-cadherin), hide without calcium and warn about both breasts. ## Test yourself Think of the answer, then tap the question to see it. ## Which protein is lost in LCIS and why does it matter? E-cadherin; without it the cells are discohesive, which explains the growth pattern of LCIS and invasive lobular carcinoma. ## How is classic LCIS usually found? Incidentally, in a biopsy done for another reason, because it forms no mass or calcifications. ## Which breast is at risk in a woman with LCIS? Both breasts; the risk of invasive carcinoma rises bilaterally. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/lobular-carcinoma-in-situ/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Breast: ducts, lobules and changes with life stage](https://durgical.com/en/histology/breast-ducts-lobules-and-changes-with-life-stage/) ## Connections ## Related 6 - [Ductal carcinoma in situ and Paget disease of the nipple](https://durgical.com/en/general-pathology/ductal-carcinoma-in-situ-and-paget-disease-of-the-nipple/) - [Atypical breast hyperplasia and cancer risk](https://durgical.com/en/general-pathology/atypical-breast-hyperplasia-and-cancer-risk/) - [Invasive breast carcinoma: special types](https://durgical.com/en/general-pathology/invasive-breast-carcinoma-special-types/) - [Familial breast cancer: BRCA1, BRCA2 and others](https://durgical.com/en/general-pathology/familial-breast-cancer-brca1-brca2-and-others/) - [Dysplasia and carcinoma in situ](https://durgical.com/en/general-pathology/dysplasia-and-carcinoma-in-situ/) - [Immunohistochemistry: the principle and the markers to know](https://durgical.com/en/general-pathology/immunohistochemistry-the-principle-and-the-markers-to-know/) ## Related conditions 2 - [Breast cancer](https://durgical.com/en/conditions/breast-cancer/) - [Hereditary breast and ovarian cancer syndrome (BRCA1/BRCA2)](https://durgical.com/en/conditions/hereditary-breast-and-ovarian-cancer-syndrome/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Breast Cancer Treatment (PDQ®)–Health Professional Version](https://www.cancer.gov/types/breast/hp/breast-treatment-pdq) (National Cancer Institute, 2026); [Genetics of Breast and Gynecologic Cancers (PDQ®)–Health Professional Version](https://www.cancer.gov/types/breast/hp/breast-ovarian-genetics-pdq) (National Cancer Institute, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/lobular-carcinoma-in-situ/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/lobular-carcinoma-in-situ/