Print Overview Breast anatomy Enlarge image Close Breast anatomy Breast anatomy Each breast contains 15 to 20 lobes of glandular tissue, arranged like the petals of a daisy. The lobes are further divided into smaller lobules that produce milk for breastfeeding. Small tubes, called ducts, conduct the milk to a reservoir that lies just beneath your nipple. Ductal carcinoma in situ (DCIS) is the presence of abnormal cells inside a milk duct in the breast. DCIS is considered the earliest form of breast cancer. DCIS is noninvasive, meaning it hasn't spread out of the milk duct and has a low risk of becoming invasive. DCIS is usually found during a mammogram done as part of breast cancer screening or to investigate a breast lump. While DCIS isn't an emergency, it does require an evaluation and a consideration of treatment options. Treatment may include breast-conserving surgery combined with radiation or surgery to remove all of the breast tissue. A clinical trial studying active monitoring as an alternative to surgery may be another option.Products & ServicesA Book: Beyond Breast CancerA Book: Mayo Clinic Family Health Book, 5th EditionMayo Clinic Comprehensive Cancer CenterNewsletter: Mayo Clinic Health Letter — Digital EditionShow more products from Mayo Clinic SymptomsDCIS doesn't typically have any signs or symptoms. However, DCIS can sometimes cause signs such as: A breast lump Bloody nipple discharge DCIS is usually found on a mammogram and appears as small clusters of calcifications that have irregular shapes and sizes. When to see a doctorMake an appointment with your doctor if you notice a change in your breasts, such as a lump, an area of puckered or otherwise unusual skin, a thickened region under the skin, or nipple discharge. Ask your doctor when you should consider breast cancer screening and how often it should be repeated. Most groups recommend considering routine breast cancer screening beginning in your 40s. Talk with your doctor about what's right for you. Request an appointment CausesIt's not clear what causes DCIS. DCIS forms when genetic mutations occur in the DNA of breast duct cells. The genetic mutations cause the cells to appear abnormal, but the cells don't yet have the ability to break out of the breast duct. Researchers don't know exactly what triggers the abnormal cell growth that leads to DCIS. Factors that may play a part include your lifestyle, your environment and genes passed to you from your parents. Risk factorsFactors that may increase your risk of DCIS include: Increasing age Personal history of benign breast disease, such as atypical hyperplasia Family history of breast cancer Never having been pregnant Having your first baby after age 30 Having your first period before age 12 Beginning menopause after age 55 Genetic mutations that increase the risk of breast cancer, such as those in the breast cancer genes BRCA1 and BRCA2 By Mayo Clinic Staff Request an appointment Diagnosis & treatment May 18, 2022 Print Living with ductal carcinoma in situ (dcis)? Connect with others like you for support and answers to your questions in the Breast Cancer support group on Mayo Clinic Connect, a patient community. Breast Cancer Discussions Concerned about the side effects of anastrozole 1915 Replies Wed, Apr 17, 2024 chevron-right Right breast cancer DCIS: Is 4-5 weeks of radiation normal protocol? 88 Replies Wed, Apr 17, 2024 chevron-right Letrozole: When will I start feeling/seeing side effects? 127 Replies Wed, Apr 17, 2024 chevron-right See more discussions Show references Niederhuber JE, et al., eds. Cancer of the breast. In: Abeloff's Clinical Oncology. 5th ed. Philadelphia, Pa.: Churchill Livingstone Elsevier; 2014. https://www.clinicalkey.com. Accessed April 27, 2018. Townsend CM Jr, et al. Diseases of the breast. In: Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice. 20th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed April 27, 2018. Breast cancer. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/f_guidelines.asp. Accessed April 27, 2018. AskMayoExpert. Ductal carcinoma in situ (DCIS): Diagnosis to first treatment (adult). Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2017. Collins LC, et al. Breast ductal carcinoma in situ: Epidemiology, clinical manifestations, and diagnosis. https://www.uptodate.com/contents/search. Accessed May 9, 2018. Distress management. Fort Washington, Pa.: National Comprehensive Cancer Network. http://www.nccn.org/professionals/physician_gls/f_guidelines.asp. Accessed April 27, 2018. What is the COMET study? DCISoptions.org. https://dcisoptions.org/comet. Accessed May 23, 2018. 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