Home
Breast & breast cancer
Breast cancer Benign breast conditions Prophylactic mastectomy
Breast reconstruction
All techniques Implant reconstruction Latissimus dorsi flap DIEP flap (abdomen) Gracilis flap (thigh) Breast lipofilling Going flat Intimate surgery
Benign gynaecological surgery
Uterus Tubes and ovaries Cervix Vulva and vagina
Gynaecological cancers
Cervical cancer Ovarian cancer Uterine cancer Vulvar cancer Borderline tumours Articles About
Request a callback Book on Doctolib →
Ductal carcinoma in situ of the breast — cancer cells confined inside a milk duct, basement membrane intact
Breast cancer · Patient guide

Ductal carcinoma in situ: breast cancer at its earliest stage

Ductal carcinoma in situ (DCIS) is an “in situ”, so-called “stage 0” breast cancer: the abnormal cells remain confined inside the milk ducts and have not crossed the wall that separates them from the rest of the breast. It does not spread to distant organs — but it is treated, because over time it can progress to an invasive cancer. Most often, it is discovered through microcalcifications on a screening mammogram.

📍 Paris 8e · Neuilly ✅ Surgery & second opinion 📞 +33 1 58 05 11 24
Have you just been diagnosed with a carcinoma in situ?
Reviewing your DCIS and your options

If a biopsy has shown ductal carcinoma in situ, or if you would like a second opinion on the surgical management, Dr Zeitoun, breast surgeon, sees patients at his practice (Paris 8e) and at Clinique Hartmann (Neuilly).

Book an appointment → Request a callback

Written and medically reviewed by Dr Jérémie Zeitoun, breast surgeon, formerly at Institut Gustave Roussy and Institut Curie. Last updated 27 July 2026.

Ductal carcinoma in situ (DCIS) is the most common form of “in situ” breast cancer — that is, a non-invasive cancer. The cells have become cancerous, but they remain trapped inside the ducts (the milk ducts) and have not crossed their wall, the basement membrane. As long as they have not crossed this boundary, they can neither invade the breast nor spread elsewhere.

This is why it is called “stage 0”: DCIS does not spread to distant organs. The prognosis is excellent. It accounts for roughly 10 to 15% of breast cancers diagnosed, and the great majority are found through screening, as microcalcifications, before any symptom.

If it is nonetheless treated, it is because a DCIS left in place can progress, over the years, to an invasive cancer, which is itself potentially dangerous. This article explains what DCIS is, how it is found, and what the treatment options are.

Diagram comparing a carcinoma in situ (cells confined within the duct, basement membrane intact) and an invasive cancer (cells having crossed the basement membrane)
Left, a carcinoma in situ: the cancer cells stay inside the duct, the basement membrane is intact. Right, an invasive cancer: the cells have crossed the wall and reach the surrounding tissue.

Need treatment for a DCIS?

Explanation of your diagnosis, choice of surgery (breast-conserving or mastectomy), surgical second opinion: a direct consultation with the breast surgeon.

Book on Doctolib Real-time availability Request a callback
DEFINITION & MECHANISM

Understanding carcinoma in situ

The breast is criss-crossed by a network of ducts (the milk ducts) that carry milk towards the nipple. The inner lining of these ducts is made of cells, separated from the rest of the breast by a thin barrier: the basement membrane. A ductal carcinoma in situ arises precisely from these cells.

The decisive boundary

“In situ”: the cells stay inside the duct

In DCIS, the cells lining the ducts have become cancerous, but they have not crossed the basement membrane: they remain “in situ”, inside the duct. And it is precisely crossing this membrane that allows a cancer to invade nearby tissue and reach the blood vessels.

As long as the membrane is intact, the cancer cannot spread to distant organs. That is the whole difference — and the good news — of an “in situ” cancer compared with an invasive cancer.

Diagram of a milk duct filled with ductal carcinoma in situ cells, with the basement membrane intact

Why treat it?

Because DCIS is a precursor: left in place, it can, over the years, turn into an invasive cancer. Today, we cannot predict with certainty which cases of DCIS will progress and which would remain stable — hence the precautionary principle.

Treating a DCIS is curative: it removes the lesion completely. This is a different situation from an already invasive cancer, where management must also take into account the risk of spread to distant organs.

DCIS, LCIS and invasive cancer: how to tell them apart

Several closely related terms appear on pathology reports and are easily confused.

→DCIS — ductal carcinoma in situ: cancer cells confined within the ducts. A true cancer, but non-invasive. This is the subject of this article.
→LCIS — lobular carcinoma in situ: a proliferation within the lobules. Regarded mainly as a risk marker, it is grouped with benign breast conditions and most often calls for simple monitoring.
→Invasive cancer — the cells have crossed the basement membrane and reached the surrounding tissue. This is the form that can involve the lymph nodes and spread to distant organs.
→Microinvasion — a DCIS with a tiny focus (≤ 1 mm) that has crossed the membrane. It still carries a very good prognosis, but changes some decisions (see below).
PATHOLOGY · THE GRADE

The grades of DCIS

Not all cases of DCIS are alike. The pathologist describes the lesion by its nuclear grade — the more or less abnormal appearance of the nucleus of the cells seen under the microscope. Three levels are distinguished, often together with the presence or absence of necrosis.

Low grade

The cell nuclei are only slightly altered, still close to normal. This is the most indolent profile — the one studied in surveillance trials.

Nuclei slightly abnormal

Intermediate grade

A nuclear appearance midway between low and high grade. Management remains surgical, tailored to the size of the lesion and the margins.

Intermediate

High grade

The nuclei are markedly abnormal, often with necrosis at the centre of the duct — this is called comedocarcinoma. This profile recurs more readily and points towards complete treatment.

Very abnormal nucleiPossible necrosis

👉 This nuclear grade is specific to DCIS: it describes the appearance of the cells and must not be confused with the SBR grade used for invasive cancers. Together with the size of the lesion and the state of the margins, it helps to choose the treatment.

HOW IT IS FOUND

The diagnosis: from microcalcifications to biopsy

In the vast majority of cases, DCIS cannot be seen or felt: it is asymptomatic. It is screening that reveals it, often years before it would become invasive — which explains its excellent prognosis.

A cluster of microcalcifications on a mammogram, the most common sign of ductal carcinoma in situ
Fine microcalcifications, clustered together: the most common sign of DCIS on a screening mammogram.

Microcalcifications

DCIS most often shows up as fine microcalcifications clustered together on the mammogram — tiny calcium deposits, invisible to the eye and impalpable. More rarely, it appears as a small mass or a nipple discharge.

A mammogram scored ACR 4 or 5

Faced with a suspicious cluster, the radiologist scores the image ACR 4 or 5 and often takes magnified views. This classification expresses the level of suspicion and leads to sampling the area. Understanding the ACR / BI-RADS classification →

Stereotactic vacuum-assisted biopsy

A definite diagnosis rests on a biopsy. Because microcalcifications are only visible on imaging, a mammography-guided vacuum-assisted biopsy (stereotaxis) is used: under local anaesthetic, several small samples are taken from the cluster. The breast biopsy, step by step →

Examination under the microscope

The pathologist confirms the DCIS and specifies its grade and the possible presence of necrosis. It is this report, discussed at a multidisciplinary team meeting, that underpins the treatment strategy. Understanding your pathology report →

Stereotactic vacuum-assisted breast biopsy guided by mammography to sample a cluster of microcalcifications suspicious for ductal carcinoma in situ
Stereotactic vacuum-assisted biopsy: under local anaesthetic, the samples are guided by mammography, precisely at the level of the microcalcification cluster.

A work-up sometimes completed by an MRI. A breast MRI may be requested to assess the true extent of the DCIS before surgery, especially if the lesion appears large or high grade: it helps to choose between breast-conserving surgery and mastectomy.

MANAGEMENT

The treatments for DCIS

Treatment of DCIS is surgical: to remove the lesion completely. It rests on two reference strategies — breast-conserving surgery followed by radiotherapy, or mastectomy without radiotherapy. One point straight away: there is no chemotherapy for a pure DCIS, since it is not invasive.

Lumpectomy + radiotherapy

Only the affected area is removed, with a margin of healthy tissue around it (lumpectomy / wide local excision), keeping the breast — then radiotherapy to the breast completes the treatment. The aim is to obtain clear margins (an international consensus sets 2 mm); otherwise, further surgery may be needed. Lumpectomy or mastectomy? →

Mastectomy (without radiotherapy)

When the DCIS is extensive, multifocal or too large relative to the breast, complete removal (mastectomy) is offered, with or without reconstruction and without radiotherapy. Reconstruction can be immediate or delayed.

The sentinel lymph node

With breast-conserving surgery, the sentinel lymph node is not performed. However, in case of mastectomy, it is taken during the same operation: if the final analysis of the removed breast were to reveal an invasive cancer, it would no longer be possible to assess it once the breast has been removed.

The multidisciplinary team meeting

Every DCIS case is discussed at a multidisciplinary team meeting (MDT), bringing together surgeon, radiologist, pathologist, oncologist and radiation oncologist. The resulting proposal is then explained and decided together with you.

👉 None of these decisions is automatic. The choice between lumpectomy followed by radiotherapy and mastectomy depends on your lesion (size, grade, margins), on your breast and on your preferences. Everything is discussed in consultation.

AFTER TREATMENT · PROGNOSIS

After treatment, and prognosis

This is the most important message: the prognosis of a treated DCIS is excellent. It is a cancer caught at its very first stage, before it has become invasive.

Follow-up consultation after ductal carcinoma in situ: explaining mammographic surveillance
Follow-up of DCIS rests mainly on regular mammographic surveillance, of the treated breast as well as the other one.

Follow-up after DCIS

→An annual mammogram is the rule after conservative treatment, to monitor the treated breast as well as the other side.
→The risk of recurrence mainly concerns the treated breast; complete surgery and radiotherapy greatly reduce it.
→If a recurrence occurs, it is roughly half the time again “in situ”, half the time invasive — hence the value of follow-up that detects it early.

Towards de-escalation? The question of active surveillance

Since some low-grade cases of DCIS may never become invasive, research is now testing active surveillance — monitoring rather than operating straight away — in this specific profile. Several large international trials (LORIS, LORD, COMET) are evaluating this strategy.

As of today, active surveillance is not yet a standard: outside these trials, surgical treatment remains recommended. But it is a promising avenue to avoid, in the future, over-treating certain patients.

Frequently asked questions

The questions that come up most often about ductal carcinoma in situ. If yours is not here, do ask it at your appointment — or to Sophie, the site assistant, at the bottom right.

Is DCIS a “real” cancer?

Yes, in the sense that the cells have indeed become cancerous. But it is an “in situ”, non-invasive cancer: the cells stay confined within the ducts and have not crossed the basement membrane. It is called “stage 0”. It is a form with a very good prognosis, not to be confused with an invasive cancer.

Can a carcinoma in situ spread to distant organs?

No. As long as the cells remain in situ, inside the ducts, they can neither reach the axillary lymph nodes nor spread to distant organs. A pure DCIS does not spread. The risk, in the long term and if it is not treated, is that it progresses to an invasive cancer.

How is DCIS found?

Most often through screening: microcalcifications clustered on a mammogram, with no symptoms at all. The radiologist then scores the image ACR 4 or 5, and the diagnosis is confirmed by an imaging-guided vacuum-assisted biopsy. More rarely, DCIS shows up as a mass or a nipple discharge.

Does the whole breast have to be removed?

No, quite the opposite. The reference treatment is most often breast-conserving: only the affected area is removed with a safety margin, keeping the breast (lumpectomy), followed by radiotherapy. Mastectomy is reserved for DCIS that is extensive, multifocal or too large relative to the breast. The decision is made together with you. Lumpectomy or mastectomy?

Do the lymph nodes have to be removed?

Not with breast-conserving surgery: a pure DCIS does not reach the lymph nodes. A sentinel lymph node is performed mainly in case of mastectomy — in case the analysis of the removed breast were to reveal an invasive cancer, since it would then no longer be possible to assess it. There is never an upfront axillary clearance for a DCIS.

Is there chemotherapy for DCIS?

No. As DCIS is non-invasive, there is no chemotherapy. Treatment rests on surgery, completed by radiotherapy in the case of breast-conserving surgery.

What is the risk of it coming back?

A risk of recurrence exists but it is greatly reduced by complete treatment (clear margins and radiotherapy, or mastectomy). When a recurrence occurs, it mainly affects the treated breast and is split roughly half as an “in situ” recurrence, half as an invasive cancer. This is the whole value of annual mammographic surveillance, which detects it early.

Further reading

To go further in understanding your diagnosis and your management.

Imaging

Mammogram scored ACR 4 or 5

What the ACR / BI-RADS classification means, what happens after an image scored 4 or 5, and why a biopsy is offered.

 Surgery

Lumpectomy or mastectomy?

The two operations, the criteria for choosing, reconstruction and special situations — for an informed surgical decision.

 Surgery

The sentinel lymph node

The principle of the sentinel lymph node, who it is for, how the operation goes and when an axillary clearance is still needed.

 Pathology report

Understanding your pathology

Grade, margins, lesion size, histological type: decoding the pathology report after a breast biopsy or surgery.
SOURCES & REFERENCES

Sources

This article draws on French guidelines and the major reference publications on ductal carcinoma in situ.

→Institut National du Cancer (INCa) — Breast cancer treatments: ductal carcinoma in situ (e-cancer.fr).
→Haute Autorité de Santé (HAS) — In situ breast cancer: guidelines and patient guide (has-sante.fr).
→Morrow M. et al. — SSO-ASTRO-ASCO Consensus on Margins for Breast-Conserving Surgery in DCIS (2 mm margin), 2016.
→EORTC 10853 and NSABP B-17 / B-24 trials — role of radiotherapy after breast-conserving surgery for DCIS.
→LORIS, LORD and COMET trials — active surveillance for low-grade DCIS.

Diagnosed with DCIS? Let’s talk it through

If a biopsy has shown ductal carcinoma in situ, or if you would like a second opinion on the surgical management, Dr Jérémie Zeitoun, breast surgeon, sees patients at his practice in the 8th arrondissement of Paris and at Clinique Hartmann in Neuilly-sur-Seine.

Book on Doctolib Scheduled consultation Request a callback
FR EN