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Lobular carcinoma in situ (LCIS) is a type of breast change that is sometimes seen when a breast biopsy is done. In LCIS, cells that look like cancer cells are growing in the lining of the milk-producing glands (lobules) of the breast, but they don’t invade through the wall of the lobules.
LCIS is not considered cancer, and it typically does not spread beyond the lobule (that is, it doesn't become invasive breast cancer) if it isn’t treated. But having LCIS does increase your risk of later developing an invasive breast cancer in either breast. (See "How does LCIS affect breast cancer risk?")
LCIS and another type of breast change (atypical lobular hyperplasia, or ALH) are types of lobular neoplasia. These are benign (non-cancerous) conditions, but they both increase your risk of breast cancer.
The different types of LCIS are:
Classic LCIS usually doesn't cause a lump that can be felt or changes that can be seen on a mammogram, although pleomorphic and florid LCIS are sometimes found this way. Most often, LCIS is found when a breast biopsy is done for another problem that’s nearby. (During a biopsy, small pieces of breast tissue are removed and checked in the lab.)
You can learn more about pathology reports showing LCIS in Understanding Your Pathology Report: Lobular Carcinoma In Situ.
Women with LCIS have about a 7 to 12 times higher risk of developing invasive cancer in either breast. For this reason, doctors typically recommend that women with LCIS have regular breast cancer screening tests and follow-up visits with a health care provider for the rest of their lives.
Having LCIS does increase your risk of developing invasive breast cancer later on. But since LCIS is not a true cancer or pre-cancer, often no treatment is needed after the biopsy.
Sometimes if LCIS is found using a needle biopsy, the doctor might recommend that it be removed completely (with an excisional biopsy or some other type of breast-conserving surgery) to help make sure that LCIS was the only abnormality there. This is especially true if the LCIS is described as pleomorphic or florid, in which case it might be more likely to grow quickly.
Even after an excisional biopsy, if pleomorphic or florid LCIS is found, some doctors might recommend another, more extensive surgery to make sure it has all been removed.
Close follow-up is important because women with LCIS have the same increased risk of developing cancer in both breasts. Women should also talk to a health care provider about what they can do to help reduce their breast cancer risk. Options for women at high risk of breast cancer because of LCIS may include:
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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National Comprehensive Cancer Network. Clinical Practice Guidelines in Oncology: Breast Cancer
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National Comprehensive Cancer Network. Clinical Practice Guidelines in Oncology: Breast Cancer Risk Reduction. Version 1.2021. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/breast_risk.pdf on October 28, 2021.
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Sabel MS, Collins LC. Atypia and lobular carcinoma in situ: High-risk lesions of the breast. UpToDate. 2021. Accessed at https://www.uptodate.com/contents/atypia-and-lobular-carcinoma-in-situ-high-risk-lesions-of-the-breast on October 28, 2021.
Last Revised: January 25, 2022