🔵 NHS & WHO sourced

DCIS — Ductal Carcinoma In Situ

DCIS (Ductal Carcinoma In Situ) is non-invasive breast cancer contained within the milk ducts. It is almost always found by screening and has an excellent outlook with treatment.

Reviewed against NHS & WHO guidelines Last reviewed: January 2025 For educational purposes — not medical advice
✓ DCIS is Stage 0 — not yet invasive cancer
✓ DCIS causes no symptoms and is almost always detected by mammogram
✓ Around 30–50% of untreated DCIS cases may progress to invasive cancer
✓ Lumpectomy followed by radiotherapy is the most common treatment

What is DCIS?

Ductal carcinoma in situ (DCIS) means abnormal cells have been found inside the milk ducts of the breast, but have not grown (invaded) through the duct wall into surrounding breast tissue. It is classified as Stage 0 — the earliest possible stage. The phrase "in situ" is Latin for "in place".

How is DCIS found?

DCIS almost always causes no symptoms. It is detected by mammogram as tiny calcium deposits (microcalcifications). DCIS was rarely diagnosed before routine mammography screening was introduced — its increased detection is one of the most significant effects of the NHS Breast Screening Programme.

Does DCIS always become invasive cancer?

Not necessarily. Estimates suggest around 30–50% of DCIS cases, if untreated, would eventually progress to invasive breast cancer. But because it is difficult to predict which cases will progress, treatment is generally recommended for all DCIS.

Treatment options

  • Surgery: Usually lumpectomy (breast-conserving) or, for widespread DCIS, mastectomy.
  • Radiotherapy: Commonly given after lumpectomy to reduce the risk of DCIS returning.
  • Hormone therapy: May be offered to reduce the risk of future breast cancer if the DCIS is hormone receptor-positive.

The debate about overtreatment

Because not all DCIS would become invasive cancer, there is ongoing clinical debate about whether all cases need treatment or whether some low-risk DCIS cases could safely be monitored. Active surveillance trials are under way. Your breast specialist can advise on whether this might be appropriate for you.

Frequently asked questions

What is DCIS and is it dangerous? +
DCIS (ductal carcinoma in situ) is Stage 0 breast cancer — abnormal cells inside the milk ducts that have not broken through the duct wall. It is not yet invasive and is almost always detected by mammogram. If untreated, around 30–50% of DCIS cases may eventually develop into invasive breast cancer, which is why treatment is generally recommended.
How is DCIS treated? +
DCIS is usually treated with surgery — lumpectomy (breast-conserving) in most cases, or mastectomy for widespread DCIS. Radiotherapy is commonly given after lumpectomy to reduce the risk of recurrence. Hormone therapy may also be offered to reduce the risk of future breast cancer if the DCIS is hormone receptor-positive.
Does DCIS always become invasive cancer? +
No. Estimates suggest around 30–50% of untreated DCIS cases would eventually progress to invasive breast cancer. But because it is difficult to predict which cases will progress — and because DCIS causes no symptoms — treatment is generally recommended for all cases to eliminate the risk of it becoming invasive.

Clinical sources

  • NHS — www.nhs.uk
  • World Health Organization — www.who.int

This content is for educational purposes and does not constitute medical advice. Always consult a qualified healthcare professional for personal medical guidance.

Continue reading

🔬

Types of Breast Cancer Explained
📊

Breast Cancer Stages and Grades
📷

Mammogram and NHS Breast Screening — What to Expect
💊

Breast Cancer Treatment Options