Patient presentation
A 55-year-old woman is referred to you after a screening mammogram showed a cluster of microcalcifications in the left breast. A stereotactic core needle biopsy confirmed ductal carcinoma in situ (DCIS). She is asymptomatic with no palpable masses.
She has no nipple discharge or retraction and no skin changes. You must take a complete history, perform a thorough breast and nodal exam, and review her imaging to plan management.
DCIS is a non-obligate precursor to invasive cancer; if untreated, roughly 25–40% will progress to invasive disease, which is the rationale for treatment. With appropriate treatment, mortality remains low at 0.5–1.0%.
What you'll be asked — and what a strong resident discusses
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What key elements of the history and physical exam are important in this patient with newly diagnosed DCIS?
Expected answer
History: family history of breast/ovarian cancer, factors of unopposed estrogen exposure (early menarche, late/no parity, late menopause), hormone replacement therapy, prior chest/neck radiation, BMI, and prior breast biopsies. Ask about any mass, nipple discharge, or retraction. Exam: detailed bilateral breast exam, expression of nipple discharge, assessment of breast size (for surgical planning), and evaluation of axillary/regional lymphadenopathy. A strong family history warrants referral for genetic counseling and testing per NCCN guidelines.
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How do you confirm the extent of disease before planning surgery?
Expected answer
Review the diagnostic and screening mammograms; 80% of DCIS is associated with calcifications, which guide but do not perfectly predict extent. Obtain additional imaging as needed (additional mammographic views, possibly MRI) to define the extent and rule out multicentric/multifocal disease. Final pathologic extent may be larger, smaller, or equal to imaging, so margins must be confirmed pathologically.
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What treatment options would you discuss with this patient and how does each affect outcomes?
Expected answer
Options are: (1) lumpectomy (excision) alone, (2) lumpectomy plus radiation +/- hormonal therapy, or (3) mastectomy. Choice of operation does not change overall survival; it affects local recurrence. Radiation reduces local recurrence by about 50%; hormonal therapy reduces it by at least 30% in ER/PR-positive patients. Choice is based on extent of disease, estimated local recurrence risk (e.g., Van Nuys index, Oncotype DCIS), and patient preference.
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What factors would make this patient a candidate for breast-conserving surgery versus mastectomy?
Expected answer
Lumpectomy is favored with a favorable breast-size-to-tumor-size ratio or amenability to oncoplastic technique, and ability to achieve clear margins. Mastectomy is favored for multicentric disease, diffuse malignant calcifications, unfavorable tumor-to-breast-size ratio, contraindications to radiation (history of prior breast/chest radiation, scleroderma or active lupus), early-to-mid pregnancy, or patient preference.
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Is sentinel lymph node biopsy indicated for this patient with pure DCIS on core biopsy?
Expected answer
No. SLNB is not indicated for pure DCIS undergoing lumpectomy, because the incidence of occult invasion is under 10% and a delayed SLNB is safe and accurate if invasion is found on final pathology. However, SLNB IS performed if the patient undergoes mastectomy, because the breast is removed and SLNB cannot be done afterward.
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What is the recommended margin for DCIS after lumpectomy, and what do you do if it is not met?
Expected answer
The consensus standard is a 2 mm margin for DCIS, which lowers local recurrence while minimizing unnecessary re-excisions. If margins are <2 mm, perform re-excision; if re-excision cannot achieve adequate margins or there is extensive residual disease, proceed to mastectomy. With margins ≥2 mm, proceed to adjuvant therapy as indicated.
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How does your management change if final pathology shows microinvasion or invasive cancer?
Expected answer
Microinvasion is defined as extension beyond the basement membrane with no focus greater than 1 mm. If invasion (or microinvasion) is found at final pathology after lumpectomy, a delayed sentinel lymph node biopsy is performed to stage the axilla. The patient is then treated as invasive breast cancer with appropriate adjuvant therapy decisions.
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Who gets radiation and hormonal therapy after breast-conserving surgery for DCIS?
Expected answer
Radiation is generally given after lumpectomy to halve local recurrence, but may be omitted in carefully selected low-risk patients (e.g., small low-grade lesion, wide margins, older patient), guided by tools like the Van Nuys index or Oncotype DCIS. Hormonal therapy (e.g., tamoxifen) is offered to ER/PR-positive patients to further reduce ipsilateral and contralateral recurrence.
What residents often miss
- Routinely ordering sentinel lymph node biopsy for pure DCIS undergoing lumpectomy when it is not indicated.
- Forgetting to perform SLNB at the time of mastectomy for DCIS, eliminating the ability to stage the axilla later.
- Failing to use image-guided/wire localization for a nonpalpable, mammographically detected lesion.
- Not obtaining a 2 mm margin and failing to re-excise inadequate margins, increasing local recurrence.
- Omitting genetic counseling referral despite a strong family history of breast/ovarian cancer.
- Recommending mastectomy or claiming a survival benefit over breast conservation—operation choice does not change overall survival.
- Overlooking contraindications to radiation (prior chest radiation, scleroderma, active lupus, pregnancy) when planning breast conservation.
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This page is educational content for general-surgery board-exam practice. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or current primary literature.