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Ductal carcinoma in situ (DCIS)
DCIS is a cancer that has not crossed the basement membrane, so it does not metastasise; the goal is to prevent local and mainly invasive relapse — excision with clear margins, usually radiation, and hormonal therapy when receptors are positive.
Why it matters in the exam
DCIS is usually found on screening mammography as calcifications, and exam questions ask when a sentinel node is needed, when radiation can be skipped, what margin width is required and why tamoxifen is given. The answers rest on understanding that the treatments reduce local relapse but do not change survival.
It matters to distinguish DCIS from invasive cancer with an intraductal component, and DCIS from LCIS — which is a risk marker and not a lesion that must be excised with clear margins. About half of relapses after breast conservation are invasive, so careful local treatment matters.
Key points
- DCIS does not cross the basement membrane and does not metastasise, so all its treatment is local, aiming to prevent relapse in the breast and mainly invasive relapse.
- Conserving surgery with 2 mm margins followed by radiation is the common treatment.
- Sentinel node only at mastectomy or when invasion is suspected.
- Tamoxifen in ER-positive disease reduces events in both breasts, with no effect on survival.
- About half of relapses are invasive — so local treatment matters.
Summary table
| Issue | Recommendation | Explanation |
|---|---|---|
| Diagnosis | Stereotactic vacuum biopsy of suspicious calcifications | Excision sometimes reveals an invasive component — mainly in a large, palpable or high-grade lesion |
| Breast-conserving surgery | Excision with margins of at least 2 mm, followed by breast radiation | Radiation cuts same-breast relapse by about half, with no change in survival |
| Mastectomy | For extensive or multicentric disease, or when clear margins cannot be achieved | A sentinel node is done at mastectomy, because it cannot be done afterwards |
| Sentinel node | Not needed in breast conservation when invasion is not suspected | Done at mastectomy, in a large or palpable lesion, or when an invasive component is suspected |
| Omitting radiation | Small lesion, low or intermediate grade, wide margins, screen-detected | Radiation still reduces relapse, but the absolute benefit is small; shared decision |
| Hormonal therapy | Tamoxifen or an aromatase inhibitor in ER-positive disease after conservation | Reduces events in the same and the opposite breast, with no survival gain |
| LCIS versus DCIS | LCIS is a marker of raised risk in both breasts and does not need clear margins | In LCIS consider preventive tamoxifen and close imaging follow-up, not radiation |
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Sources
- NCCN Clinical Practice Guidelines in Oncology: Breast Cancer, 2026 — Ductal carcinoma in situ
- SSO-ASTRO-ASCO Consensus Guideline on Margins for Breast-Conserving Surgery with Whole-Breast Irradiation in DCIS, 2016 — Margin width
- DeVita, Hellman and Rosenberg's Cancer: Principles and Practice of Oncology, 12th ed. (2023) — Malignant tumors of the breast
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.