Ductal carcinoma in situ

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

DCIS is a pathological diagnosis of malignant ductal cells without stromal invasion. It is heterogeneous in grade, extent and progression potential. High-grade lesions often show central necrosis and fine linear or branching calcification; low-grade disease may appear as more indolent grouped calcification. Because needle sampling covers only part of the radiological field, the clinical task is not only to confirm DCIS but also to define its extent and estimate whether invasion has been missed.

Mammography maps calcification and guides stereotactic biopsy. Ultrasound is added for a mass or node, and MRI is reserved for selected extent or occult questions because enhancement can overestimate disease. The specimen radiograph proves that the calcification target was retrieved. Final surgical pathology examines the whole lesion, margins and any invasive focus. Pure DCIS needs neither distant staging nor systemic anticancer staging investigations.

Local treatment prevents future in-breast DCIS and invasive cancer. Conservation removes the radiological field and is normally followed by breast radiotherapy. Mastectomy treats extensive disease and has a very low local-recurrence risk. Axillary staging is omitted during conservation for pure DCIS but accompanies mastectomy because an unsuspected invasive focus cannot be followed later by standard sentinel mapping. Any proven invasion returns the case to the early invasive breast pathway.

Endocrine treatment is risk reduction rather than treatment of an existing invasive clone. Tamoxifen or an aromatase inhibitor in an appropriate postmenopausal patient can reduce new ipsilateral and contralateral events after breast-conserving treatment for ER-positive DCIS. Choice weighs age, menopause, VTE and uterine risk, bone health, symptoms and absolute benefit. Chemotherapy is inappropriate because intact basement membrane prevents systemic dissemination.

Key points

DCIS consists of malignant epithelial cells confined within breast ducts by an intact myoepithelial layer and basement membrane; pure DCIS cannot metastasise.
Most cases are detected as mammographic microcalcification rather than a palpable lump, but a mass or nipple discharge increases concern for more extensive disease or occult invasion.
Stereotactic or tomosynthesis-guided vacuum-assisted sampling is preferred for many calcification-only lesions because it obtains representative tissue and confirms that target calcification was removed.
Pathology should report nuclear grade, necrosis, size or extent where assessable, margins after surgery and ER when endocrine risk reduction is being considered.
Do not request routine CT, bone scan or PET-CT for pure DCIS; systemic staging adds radiation and false positives without a metastatic mechanism.
Breast-conserving surgery is appropriate when the radiological field can be excised with clear margins and an acceptable breast result; radiotherapy usually follows to reduce local recurrence.
Mastectomy is appropriate for diffuse or multicentric extent, inability to achieve margins, an unfavourable lesion-to-breast ratio or informed preference and usually cures local disease without postoperative radiotherapy.
Do not perform routine sentinel-node biopsy with breast-conserving surgery for pure DCIS. Offer it with mastectomy because lymphatic mapping cannot be performed reliably afterwards if invasion is discovered.
Endocrine treatment after breast-conserving therapy for ER-positive DCIS can reduce ipsilateral and contralateral breast events but does not treat distant disease or replace surgery.
Chemotherapy and HER2-directed therapy have no role in pure DCIS; if invasion is found, reclassify and treat the invasive component.
Explain absolute recurrence reduction and competing treatment harms because a screen-detected non-invasive lesion can otherwise feel indistinguishable from metastatic-risk cancer.
Continue mammographic surveillance after conservation and after unilateral mastectomy of the remaining breast, with prompt diagnostic assessment of new symptoms.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Age and hormonal exposure

Risk rises with age and shares reproductive, alcohol, obesity and exogenous-hormone associations with invasive breast cancer because both arise from mammary epithelium.

Inherited susceptibility

Pathogenic breast-cancer variants and strong family history increase pre-invasive and invasive tumour risk and may alter bilateral imaging and surgical decisions.

Acquired ductal genomic change

Somatic alterations create clonal epithelial proliferation within a duct–lobular system, with molecular patterns overlapping the invasive subtype that may later emerge.

Detection through screening

Population mammography identifies otherwise occult calcification, so incidence reflects both underlying biology and the intensity and sensitivity of radiological detection.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Malignant cells remain in ducts
Atypical clonal epithelial cells fill and distort terminal duct–lobular units while the myoepithelial layer and basement membrane remain intact.
2
Necrosis creates calcification
High-grade rapid proliferation can outgrow luminal blood supply, producing comedo necrosis and linear or branching microcalcification visible on mammography.
3
Progression potential is heterogeneous
Some low-grade lesions may remain indolent for years, whereas high-grade, larger or biologically adverse lesions have greater risk of ipsilateral invasive recurrence.
4
Invasion unlocks metastatic access
Pure DCIS lacks stromal and lymphovascular access and therefore does not metastasise; occult microinvasion or invasive foci change nodal and systemic considerations.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Screen-detected calcification

Fine pleomorphic, linear or branching calcification in a segmental or ductal distribution is the classic radiological presentation requiring stereotactic tissue.

Palpable DCIS

A mass, density or distortion can accompany extensive in-duct disease but raises the chance of coexisting invasion and requires ultrasound and core assessment.

Nipple presentation

Bloody single-duct discharge or Paget-like change may reflect central DCIS, papilloma or invasive malignancy and needs targeted examination and imaging.

High upgrade risk

Large extent, high grade, comedo necrosis, a mass, imaging–pathology discordance or limited sampling increases the probability of invasion at surgery.

Unexpected invasive diseaseRed flag

Microinvasion or stromal invasion on excision changes nodal, receptor, systemic and sometimes margin decisions and requires prompt MDT restaging.

Red flags requiring action

A palpable mass, architectural distortion, suspicious node or extensive high-grade calcification increases the probability that biopsy has under-sampled invasive cancer.
New bloody single-duct discharge, nipple retraction or Paget-like nipple change may represent extensive ductal disease or an occult invasive component.
Rapid postoperative swelling, severe pain, hypotension or high drain output suggests haemorrhage requiring immediate surgical review.
Fever, spreading erythema, purulent drainage or implant exposure after surgery requires urgent infection and source-control assessment.
Positive or very close margins after repeated excision require specialist review because residual field disease and further cosmetic harm may favour mastectomy.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line diagnostic mammography with magnificationFirst stepFirst line
Why
Characterise morphology and distribution of calcification and estimate the full field requiring biopsy and excision.
Interpretation and limitations
Compare with prior images, document maximum span and separate groups and recognise that apparent radiological size can under- or overestimate pathological extent.
02
Preferred stereotactic vacuum-assisted biopsyPreferred
Why
Sample calcification widely enough to diagnose grade and assess for invasive or atypical components.
Interpretation and limitations
Confirm calcification in the specimen radiograph and clip the site; normal tissue or non-retrieval of the target is discordant and requires repeat sampling.
03
Targeted ultrasound and node assessment
Why
Evaluate an associated mass, duct change or suspicious axillary node and provide an alternative biopsy route.
Interpretation and limitations
A solid component or abnormal node increases concern for invasion; pure calcification-only DCIS may have no ultrasound correlate.
04
Selective breast MRI
Why
Clarify extent or occult disease when dense tissue, discordant size, lobular features or surgical planning creates a specific unanswered question.
Interpretation and limitations
Do not convert to mastectomy for MRI enhancement alone; obtain second-look or MRI-guided tissue from findings that would change surgery.
05
Definitive excision histologyDefinitive
Why
Measure extent, grade, necrosis and margins and detect microinvasion or invasive carcinoma across the resection.
Interpretation and limitations
Use specimen orientation and imaging correlation; invasion triggers ER and HER2 assessment and consideration of nodal staging and systemic treatment.
06
ER testing for preventive treatment
Why
Identify whether adjuvant endocrine risk reduction can affect residual ipsilateral or contralateral hormone-sensitive events.
Interpretation and limitations
ER positivity supports a discussion rather than mandates therapy; benefit is preventive and must be balanced against VTE, uterine, bone and menopausal toxicity.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Atypical ductal hyperplasia

A limited low-grade clonal proliferation may be morphologically similar but smaller in extent; sampling adequacy and upgrade risk guide excision.

Lobular neoplasia

Atypical lobular hyperplasia and lobular carcinoma in situ show discohesive E-cadherin-negative cells and act largely as bilateral risk markers with distinct management.

Benign calcification

Secretory, vascular, dermal, fat-necrosis and fibroadenoma calcifications have characteristic patterns, but evolving or pleomorphic groups need image-guided tissue.

Invasive carcinoma

Stromal invasion, desmoplasia, a mass or suspicious node changes prognosis and introduces receptor-directed systemic and axillary treatment decisions.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01CalcificationSample the complete radiological targetFirst stepScreening or symptomatic mammography identifies suspicious calcification without proven invasion.

1Obtain diagnostic magnification views, map number and span of groups and add ultrasound when a mass, duct or node is present.
2Perform stereotactic or tomosynthesis-guided vacuum-assisted biopsy, confirm target calcification in the cores and place a marker for later localisation.
3Review radiological and pathological concordance at the breast MDT and repeat sampling when tissue does not adequately explain the imaging category.

02ConservationExcise clearly and reduce in-breast recurrenceThe DCIS field is suitable for breast-conserving surgery with an acceptable expected cosmetic result.

1Localise and excise the full calcification field, using specimen imaging and oriented margins to guide immediate or later additional surgery.
2Re-excise a clinically important involved margin or discuss mastectomy when repeated clear excision would leave poor form or extensive residual disease.
3Offer postoperative breast radiotherapy according to recurrence risk and discuss endocrine risk reduction for ER-positive disease after absolute-benefit and toxicity review.

03MastectomyStage the axilla only when future mapping mattersDiffuse extent, margin failure, lesion-to-breast ratio or preference leads to mastectomy for biopsy-proven DCIS.

1Confirm extent and reconstruction preference and explain the high local control, altered sensation and usually absent need for postoperative radiotherapy.
2Perform sentinel lymph-node biopsy at the same operation because occult invasion may be found and reliable sentinel mapping is not available after breast removal.
3Review final pathology; if disease remains pure DCIS with clear margins, avoid chemotherapy and routine systemic staging, while invasion enters the appropriate invasive pathway.

04SurveillanceMonitor the remaining breast tissueLocal treatment is complete and no invasive component remains.

1Provide a pathology and treatment summary, mammography schedule and explanation of residual ipsilateral or contralateral risk based on the operation performed.
2Review endocrine risk-reduction adherence and VTE, uterine, bone, joint and menopausal effects if treatment was chosen.
3Arrange immediate symptomatic triple assessment for a new lump, discharge, nipple or skin change rather than waiting for the next surveillance image.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Reduces subsequent ipsilateral and contralateral hormone-sensitive breast events but does not compensate for inadequate excision or replace radiotherapy when indicated.

Tamoxifen after ER-positive DCIS

Give tamoxifen 20 mg orally once daily, commonly for 5 years, when endocrine risk reduction is chosen after breast-conserving treatment; duration follows the individual breast-oncology plan.

Discuss venous thromboembolism, abnormal uterine bleeding, pregnancy avoidance, cataract and CYP2D6 interactions; investigate postmenopausal bleeding and balance absolute preventive benefit against toxicity.

Reduces new breast events after local treatment of ER-positive DCIS without exposing the patient to tamoxifen-related uterine and thrombotic risk.

Anastrozole after menopause

Give anastrozole 1 mg orally once daily for the planned preventive course in an appropriate postmenopausal patient when selected instead of tamoxifen.

Confirm menopause, assess bone density and fracture risk and review arthralgia, vaginal symptoms, cardiovascular factors and adherence; it is not effective alone before menopause.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Ipsilateral DCIS recurrence

Residual or new in-breast ductal disease can recur after conservation, with risk reduced by clear excision and appropriate radiotherapy.

Ipsilateral invasive cancer

A proportion of recurrences breach the basement membrane, creating nodal and distant metastatic potential and requiring invasive-cancer treatment.

Occult invasion at excision

Core biopsy samples only part of a lesion, so final surgery may reveal microinvasion or invasion and prompt receptor and nodal reassessment.

Treatment morbidity and overtreatment

Surgery, radiotherapy and endocrine prevention can cause body-image, pain, lymphatic, menopausal, thrombotic and bone harms despite no current metastatic risk.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

After conservation, review wound, haematoma, infection, margin result, specimen radiograph and final extent before declaring surgery complete.
During radiotherapy, monitor skin, breast oedema, pain and fatigue and provide later assessment for fibrosis, telangiectasia and cosmetic change.
During tamoxifen, review thrombosis and uterine symptoms and medication interactions; during aromatase inhibition, review joints, menopause and bone density.
Arrange scheduled mammography of remaining breast tissue and compare with the treated baseline, recognising expected scar and radiotherapy changes.
Record any upgrade to microinvasion or invasion and confirm that receptor, nodal and systemic decisions were re-opened rather than copied from the DCIS plan.
Monitor psychological impact and decision regret because the term carcinoma and mastectomy can feel disproportionate to a non-metastatic biological state.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

DCIS is malignant but non-invasive

The cells have cancer morphology yet lack stromal access, explaining why local recurrence matters while distant staging and chemotherapy do not.

Calcification retrieval proves targeting

A stereotactic procedure is not adequate merely because cores were obtained; the specimen image must show that the suspicious calcification was sampled.

Mastectomy changes sentinel timing

Sentinel biopsy is unnecessary in routine conservation but is performed with mastectomy because later lymphatic mapping from an absent breast is unreliable.

Endocrine therapy prevents new events

Its role is reducing future ipsilateral and contralateral disease, not eradicating distant micrometastases, which pure DCIS cannot create.

MRI requires tissue consequences

Additional enhancement should be biopsied when it would enlarge surgery; otherwise high sensitivity can turn uncertainty into unnecessary mastectomy.

Upgrade risk belongs in consent

Core biopsy may miss a nearby invasive focus, so surgery and sentinel decisions should anticipate the probability and consequences of final upgrade.

11Common pitfallsFrequent interpretation and management errors.

01
Describing pure DCIS as metastatic-risk invasive cancer or requesting routine body staging.
02
Failing to confirm calcification retrieval during image-guided biopsy.
03
Changing from conservation to mastectomy for unbiopsied MRI enhancement.
04
Performing routine sentinel-node biopsy with every breast-conserving DCIS operation.
05
Omitting sentinel-node biopsy when mastectomy removes the later opportunity and occult invasion is possible.
06
Using endocrine therapy instead of complete local excision or indicated radiotherapy.
07
Offering chemotherapy or HER2 treatment for pure DCIS.
08
Failing to re-open staging and receptor decisions when final histology shows invasion.
09
Minimising treatment morbidity because the lesion was found through screening.