{"entity":{"id":"ductal-carcinoma-in-situ","kind":"cancer","name":"Ductal carcinoma in situ (DCIS)","aka":["DCIS","Stage 0 breast cancer","Pre-invasive breast cancer","Intraductal carcinoma","stage 0 breast cancer","Tis (DCIS)","non-invasive breast cancer","in situ breast cancer","pre-invasive breast cancer","intraductal carcinoma of the breast"],"tldr":"DCIS is abnormal cells confined to the milk ducts of the breast; it is not yet invasive cancer and cannot spread, but some would become invasive if left. Lumpectomy with radiotherapy, or mastectomy, halves local recurrence, so the live question is which low-risk DCIS can safely be watched: the COMET trial (2024) found active monitoring no worse at two years.","summary":"Ductal carcinoma in situ is a non-obligate precursor of invasive breast cancer: neoplastic epithelial cells fill the ducts without breaching the basement membrane. It is almost always detected as microcalcifications on screening mammography, is graded low, intermediate or high by nuclear grade and necrosis, and is characterised by ER, PR and HER2 status. Natural-history data from misdiagnosed or untreated cases and from autopsy series show that a substantial share of low-grade DCIS never progresses, which makes overdiagnosis and overtreatment the central problem of the disease.\n\nStandard treatment is breast-conserving surgery with clear margins (2 mm) followed by whole-breast radiotherapy, which halves local recurrence (about half of recurrences being invasive) without affecting survival, or mastectomy for extensive disease; sentinel node biopsy is done only with mastectomy or suspicion of invasion. Adjuvant endocrine therapy (tamoxifen, or an aromatase inhibitor in postmenopausal women per NSABP B-35 and IBIS-II DCIS) reduces ipsilateral and contralateral events in ER-positive DCIS. Genomic assays (Oncotype DX DCIS Score, DCISionRT) and clinicopathological tools help identify women who can omit radiotherapy. Three randomised trials test active monitoring against surgery for low-risk DCIS: COMET (US; JAMA, December 2024) reported that active monitoring was non-inferior for the two-year rate of ipsilateral invasive cancer, LORIS (UK) and LORD (Netherlands, now including a patient-preference cohort) continue to follow patients. Longer follow-up is needed before monitoring becomes routine, but the results have already changed how DCIS is discussed with patients.\n\nThe frontier is a risk-stratified approach in which high-grade or HER2-positive DCIS is treated fully while low-risk lesions are watched, informed by molecular classifiers and, potentially, by preventive vaccines against HER2 or other DCIS antigens.","asOf":"2026-09-25","wikipedia":"https://en.wikipedia.org/wiki/Ductal_carcinoma_in_situ","links":[{"label":"NCI: ductal carcinoma in situ","url":"https://www.cancer.gov/types/breast/breast-cancer-types/dcis"},{"label":"COMET trial (JAMA 2024)","url":"https://doi.org/10.1001/jama.2024.26698"},{"label":"SSO-ASTRO-ASCO margin guideline for DCIS (JCO 2016)","url":"https://doi.org/10.1200/JCO.2016.68.3573"},{"label":"LORD trial (NCT02492607)","url":"https://clinicaltrials.gov/study/NCT02492607"},{"label":"Royal College of Pathologists G148: dataset for histopathological reporting of breast disease in surgical excision specimens of breast cancer, version 3, November 2024 (full review due November 2026)","url":"https://www.rcpath.org/resourceLibrary/g148-dataset-for-histopathological-reporting-of-breast-disease-in-surgical-excision-specimens-of-breast-cancer.html"},{"label":"Brierley et al., International Journal of Cancer 2026: the 9th edition of the UICC TNM classification of malignant tumours, updates and rationale for change (breast: the classification remains unchanged, the yp classification is clarified)","url":"https://doi.org/10.1002/ijc.70561"}],"tags":["nci-coverage","breast","overdiagnosis"],"related":["breast-hr-positive","breast-her2-positive","tnbc","male-breast-cancer","paget-disease-of-the-nipple","phyllodes-tumour"],"cancers":[],"sections":[],"technologies":["mammography","imrt-igrt","endocrine-therapy","active-surveillance","radiology-ai-screening","mri"],"targets":["estrogen-receptor","her2"],"drugs":["tamoxifen","oncotype-dx","mammaprint","anastrozole"],"companies":[],"institutions":[],"pathways":["er-signaling"],"terms":["dcis","carcinoma-in-situ","lumpectomy","mastectomy","in-situ","tnm-breast-cancer-editions","terminal-duct-lobular-unit","er-pr-scoring-breast","nottingham-grade"],"trials":["nsabp-b39","comet-dcis","tam-01"],"people":[],"bottlenecks":["b-overdiagnosis","b-toxicity-qol"],"keyPapers":["paper-morrow-j-clin-oncol"],"journals":[],"dependsOn":[],"notes":["Why this page and not one of the receptor pages. Ductal carcinoma in situ is staged Tis (DCIS), which is stage 0, and it has not crossed the basement membrane, so it cannot have spread. That is why the receptor subtype pages, which are about systemic treatment of invasive cancer, are not where a reader with in-situ disease should start. DCIS is graded by nuclear grade and necrosis rather than by the Nottingham system used for invasive cancer, and assessing its oestrogen receptor status is not a mandatory item of the UK dataset; it is measured when endocrine treatment is being considered, using the same cut-off as for invasive cancer for want of a separate consensus."],"group":"breast","burden":"About one in five to one in four breast cancers detected by mammographic screening is DCIS; it was rare before screening and is now diagnosed in tens of thousands of women a year in the US alone (SEER; NCI).","subtypes":["Low-grade DCIS (often ER-positive)","Intermediate-grade DCIS","High-grade DCIS with comedo necrosis (often HER2-positive)","DCIS with microinvasion (staged as T1mi)","Paget disease of the nipple (DCIS extending to nipple skin)"],"biomarkers":["Nuclear grade and necrosis","ER and PR status","HER2 status (not used to select therapy outside trials)","Margin width (2 mm standard after breast conservation)","Oncotype DX DCIS Score or DCISionRT (radiotherapy omission decisions)","Extent on mammography and MRI"],"standardOfCare":[{"setting":"Localised DCIS, breast conservation","approach":"Lumpectomy to 2 mm margins followed by whole-breast radiotherapy (hypofractionated), with radiotherapy omission considered for low-risk lesions (RTOG 9804 criteria or genomic assay).","refs":["lumpectomy","imrt-igrt","oncotype-dx"],"guideline":{"nccn":"Category 1 (radiotherapy after lumpectomy)","version":"NCCN Guidelines: Breast Cancer; SSO-ASTRO-ASCO margin guideline 2016","url":"https://doi.org/10.1200/JCO.2016.68.3573"}},{"setting":"Extensive or multicentric DCIS","approach":"Mastectomy with sentinel node biopsy and optional reconstruction; radiotherapy not needed after mastectomy with clear margins.","refs":["mastectomy","sentinel-node"],"guideline":{"version":"NCCN Guidelines: Breast Cancer"}},{"setting":"ER-positive DCIS after breast conservation","approach":"Tamoxifen (or anastrozole in postmenopausal women) for five years to reduce ipsilateral and contralateral breast events; low-dose tamoxifen is an option (TAM-01).","refs":["tamoxifen","endocrine-therapy"],"guideline":{"nccn":"Category 1 (tamoxifen); Category 2A (aromatase inhibitor)","version":"NSABP B-24, B-35; IBIS-II DCIS; TAM-01","url":"https://doi.org/10.1016/S0140-6736(15)01168-X"}},{"setting":"Low-risk DCIS","approach":"Active monitoring with mammography every six months and optional endocrine therapy, in trials (COMET, LORIS, LORD) or after shared decision-making where guidelines allow.","refs":["active-surveillance","mammography","dcis","b-overdiagnosis"],"guideline":{"version":"COMET (JAMA 2024)","url":"https://doi.org/10.1001/jama.2024.26698"}}],"stateOfArt":["COMET is the first randomised evidence that low-risk DCIS can be monitored rather than operated on, at least in the short term; LORIS and LORD will add longer follow-up.","Genomic assays and validated clinicopathological criteria let many women omit radiotherapy after lumpectomy.","Hypofractionated and partial-breast radiotherapy shorten treatment for those who need it; low-dose tamoxifen cuts side effects.","DCIS is the clearest example of the overdiagnosis problem in oncology and the test bed for risk-stratified de-escalation."],"history":[{"year":1932,"title":"Broders defines carcinoma in situ","note":"The concept of non-invasive cancer confined by the basement membrane.","refs":[]},{"year":1985,"title":"Screening mammography makes DCIS common","note":"Incidence rises several-fold in screened populations.","refs":[]},{"year":1993,"title":"NSABP B-17: radiotherapy after lumpectomy for DCIS","note":"Halves local recurrence; no survival difference.","refs":["lumpectomy"]},{"year":1999,"title":"NSABP B-24: tamoxifen after lumpectomy plus radiotherapy","refs":["tamoxifen"]},{"year":2015,"title":"Anastrozole versus tamoxifen for DCIS (NSABP B-35, IBIS-II DCIS)","note":"Aromatase inhibitor an alternative in postmenopausal women.","refs":["tamoxifen"]},{"year":2016,"title":"2 mm margin standard (SSO-ASTRO-ASCO)","refs":["lumpectomy"]},{"year":2024,"title":"COMET: active monitoring non-inferior at two years","note":"Hwang and colleagues (JAMA, December 2024); first randomised evidence for monitoring low-risk DCIS.","refs":["active-surveillance"]}],"pipeline":["active-surveillance","oncotype-dx","tamoxifen"],"openProblems":["Distinguishing DCIS that would progress from DCIS that would not; molecular classifiers, mammographic AI and the monitoring trials are the route.","Long-term safety of active monitoring beyond two years; LORIS and LORD follow-up and the COMET ten-year endpoint will tell.","Overtreatment by mastectomy remains common; shared decision aids and radiotherapy omission tools are the response.","Preventing progression pharmacologically or with vaccines (HER2-directed DCIS vaccine trials) rather than surgically."],"parent":"breast-cancer"},"route":"/cancers/ductal-carcinoma-in-situ/","neighbours":{"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"breast-her2-positive","kind":"cancer","name":"HER2-positive breast cancer","route":"/cancers/breast-her2-positive/"},{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"invasive-breast-carcinoma-no-special-type","kind":"cancer","name":"Invasive breast carcinoma of no special type (invasive ductal carcinoma)","route":"/cancers/invasive-breast-carcinoma-no-special-type/"},{"id":"invasive-cribriform-carcinoma-breast","kind":"cancer","name":"Invasive cribriform carcinoma of the breast","route":"/cancers/invasive-cribriform-carcinoma-breast/"},{"id":"lobular-carcinoma-in-situ","kind":"cancer","name":"Lobular carcinoma in situ (LCIS)","route":"/cancers/lobular-carcinoma-in-situ/"},{"id":"male-breast-cancer","kind":"cancer","name":"Male breast cancer","route":"/cancers/male-breast-cancer/"},{"id":"paget-disease-of-the-nipple","kind":"cancer","name":"Paget disease of the nipple","route":"/cancers/paget-disease-of-the-nipple/"},{"id":"papillary-carcinoma-breast","kind":"cancer","name":"Papillary carcinomas of the breast (encapsulated, solid and invasive papillary)","route":"/cancers/papillary-carcinoma-breast/"},{"id":"phyllodes-tumour","kind":"cancer","name":"Phyllodes tumour of the breast","route":"/cancers/phyllodes-tumour/"},{"id":"tnbc","kind":"cancer","name":"Triple-negative breast cancer (TNBC)","route":"/cancers/tnbc/"}],"technology":[{"id":"active-surveillance","kind":"technology","name":"Active surveillance","route":"/technologies/active-surveillance/"},{"id":"radiology-ai-screening","kind":"technology","name":"AI in radiology","route":"/technologies/radiology-ai-screening/"},{"id":"endocrine-therapy","kind":"technology","name":"Endocrine therapy (SERMs, AIs, SERDs)","route":"/technologies/endocrine-therapy/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"mammography","kind":"technology","name":"Mammography & tomosynthesis","route":"/technologies/mammography/"},{"id":"mri","kind":"technology","name":"MRI","route":"/technologies/mri/"},{"id":"sentinel-node","kind":"technology","name":"Sentinel lymph node biopsy","route":"/technologies/sentinel-node/"}],"target":[{"id":"estrogen-receptor","kind":"target","name":"Estrogen receptor (ERα)","route":"/targets/estrogen-receptor/"},{"id":"her2","kind":"target","name":"HER2","route":"/targets/her2/"}],"drug":[{"id":"anastrozole","kind":"drug","name":"Anastrozole","route":"/drugs/anastrozole/"},{"id":"mammaprint","kind":"drug","name":"MammaPrint (70-gene signature)","route":"/drugs/mammaprint/"},{"id":"oncotype-dx","kind":"drug","name":"Oncotype DX","route":"/drugs/oncotype-dx/"},{"id":"tamoxifen","kind":"drug","name":"Tamoxifen","route":"/drugs/tamoxifen/"}],"pathway":[{"id":"er-signaling","kind":"pathway","name":"Oestrogen receptor signalling","route":"/pathways/er-signaling/"}],"term":[{"id":"carcinoma-in-situ","kind":"term","name":"Carcinoma in situ (CIS)","route":"/terms/carcinoma-in-situ/"},{"id":"dcis","kind":"term","name":"Ductal carcinoma in situ (DCIS)","route":"/terms/dcis/"},{"id":"terminal-duct-lobular-unit","kind":"term","name":"Ducts, lobules and the terminal duct lobular unit","route":"/terms/terminal-duct-lobular-unit/"},{"id":"er-pr-scoring-breast","kind":"term","name":"How ER and PR are scored on a breast report (Allred score, H score, and why PR is not a UK core item)","route":"/terms/er-pr-scoring-breast/"},{"id":"in-situ","kind":"term","name":"In situ","route":"/terms/in-situ/"},{"id":"lumpectomy","kind":"term","name":"Lumpectomy (breast-conserving surgery)","route":"/terms/lumpectomy/"},{"id":"mastectomy","kind":"term","name":"Mastectomy","route":"/terms/mastectomy/"},{"id":"nottingham-grade","kind":"term","name":"Nottingham grade (breast cancer grade 1, 2 and 3)","route":"/terms/nottingham-grade/"},{"id":"partial-breast-irradiation","kind":"term","name":"Partial-breast irradiation","route":"/terms/partial-breast-irradiation/"},{"id":"breast-tumour-size-on-the-report","kind":"term","name":"Tumour size on a breast report, and why it differs from the scan","route":"/terms/breast-tumour-size-on-the-report/"},{"id":"tnm-breast-cancer-editions","kind":"term","name":"Which staging edition a breast report uses: UICC TNM 8, TNM 9 and the AJCC prognostic stage","route":"/terms/tnm-breast-cancer-editions/"}],"trial":[{"id":"comet-dcis","kind":"trial","name":"COMET (Comparison of Operative versus Monitoring and Endocrine Therapy)","route":"/trials/comet-dcis/"},{"id":"nsabp-b39","kind":"trial","name":"NSABP B-39/RTOG 0413","route":"/trials/nsabp-b39/"},{"id":"nct00769379","kind":"trial","name":"Radiation Therapy With or Without Trastuzumab in Treating Women With Ductal Carcinoma In Situ Who Have Undergone Lumpectomy","route":"/trials/nct00769379/"},{"id":"rapid","kind":"trial","name":"RAPID (accelerated partial-breast irradiation)","route":"/trials/rapid/"},{"id":"tam-01","kind":"trial","name":"TAM-01","route":"/trials/tam-01/"}],"bottleneck":[{"id":"b-overdiagnosis","kind":"bottleneck","name":"Overdiagnosis and false alarms","route":"/bottlenecks/b-overdiagnosis/"},{"id":"b-toxicity-qol","kind":"bottleneck","name":"Toxicity and quality of life are undervalued","route":"/bottlenecks/b-toxicity-qol/"}],"paper":[{"id":"paper-morrow-j-clin-oncol","kind":"paper","name":"Society of Surgical Oncology-American Society for Radiation Oncology-American Society of Clinical Oncology Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Ductal Carcinoma In Situ","route":"/key-papers/paper-morrow-j-clin-oncol/"}],"person":[{"id":"andrea-decensi","kind":"person","name":"Andrea DeCensi","route":"/people/andrea-decensi/"},{"id":"shelley-hwang","kind":"person","name":"E. Shelley Hwang","route":"/people/shelley-hwang/"}],"journal":[{"id":"breast-cancer-jbcs","kind":"journal","name":"Breast cancer","route":"/journals/breast-cancer-jbcs/"},{"id":"breast-cancer-research","kind":"journal","name":"Breast cancer research","route":"/journals/breast-cancer-research/"},{"id":"breast-cancer-research-and-treatment","kind":"journal","name":"Breast cancer research and treatment","route":"/journals/breast-cancer-research-and-treatment/"},{"id":"clinical-breast-cancer","kind":"journal","name":"Clinical breast cancer","route":"/journals/clinical-breast-cancer/"},{"id":"journal-of-breast-imaging","kind":"journal","name":"Journal of breast imaging","route":"/journals/journal-of-breast-imaging/"},{"id":"journal-of-mammary-gland-biology-and-neoplasia","kind":"journal","name":"Journal of mammary gland biology and neoplasia","route":"/journals/journal-of-mammary-gland-biology-and-neoplasia/"},{"id":"the-breast","kind":"journal","name":"The Breast","route":"/journals/the-breast/"},{"id":"the-breast-journal","kind":"journal","name":"The breast journal","route":"/journals/the-breast-journal/"}]}}