# Ductal carcinoma in situ (DCIS)

Source: https://onco.cc/terms/dcis/  
OnCo record `dcis` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Breast cancer cells confined inside the milk ducts, found mostly by mammography as calcifications. It is not life-threatening in itself, but around a third would progress to invasive cancer if left.

## Summary

DCIS makes up 20-25% of screen-detected breast cancers. Standard treatment is lumpectomy with radiotherapy (or mastectomy for extensive disease) plus tamoxifen or an aromatase inhibitor if ER-positive; low-dose tamoxifen (5 mg, TAM-01) halves recurrence with fewer side effects. Because many DCIS lesions are indolent, active surveillance trials (COMET, LORIS, LORD) tested omitting surgery for low-risk disease, and COMET found no excess invasive cancer at 2 years. It is a leading example of the overdiagnosis debate in screening.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: DCIS; ductal carcinoma in situ; ductal in situ

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Ductal_carcinoma_in_situ
- Wikipedia: https://en.wikipedia.org/wiki/Ductal_carcinoma_in_situ

## Connected records

- terms: [Active surveillance and observation](https://onco.cc/terms/active-surveillance-term/), [Carcinoma in situ (CIS)](https://onco.cc/terms/carcinoma-in-situ/), [Lumpectomy (breast-conserving surgery)](https://onco.cc/terms/lumpectomy/)
- technologies: [Active surveillance](https://onco.cc/technologies/active-surveillance/), [Breast MRI coils and abbreviated breast MRI](https://onco.cc/technologies/breast-mri-coils-abbreviated-mri/), [Contrast-enhanced mammography](https://onco.cc/technologies/contrast-enhanced-mammography/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Ductal carcinoma in situ (DCIS)](https://onco.cc/cancers/ductal-carcinoma-in-situ/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- fronts: [Early Detection & Screening](https://onco.cc/fronts/early-detection/)
- drugs: [Tamoxifen](https://onco.cc/drugs/tamoxifen/)

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JSON: https://onco.cc/api/v1/entities/dcis.json