Ductal Carcinoma In Situ (DCIS): Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Ductal carcinoma in situ (DCIS) is a non-invasive breast neoplasm in which malignant epithelial cells are confined within breast ducts without invasion through the basement membrane. It accounts for approximately 20-25% of newly diagnosed breast cancers in the US (~50,000 cases per year), detected almost exclusively by mammographic screening (microcalcifications).

Risk factors mirror those of invasive breast cancer: increasing age (peak 50-59), family history, BRCA1/2 germline mutations (DCIS risk approximately 40-60% lifetime), prior biopsy showing atypical ductal hyperplasia (ADH), dense breast tissue, nulliparity, late menopause, and prolonged hormone replacement therapy. DCIS shares molecular pathways with invasive breast cancer.

The vast majority of DCIS is asymptomatic, detected only on routine screening mammography as microcalcifications, architectural distortion, or soft tissue density. Occasionally presents as nipple discharge (bloody or serous), a palpable lump, or Paget's disease of the nipple (eczematous nipple changes representing DCIS of the large ducts). In the modern screening era, symptomatic DCIS is uncommon.

Diagnostic mammography characterizes calcification morphology (amorphous, pleomorphic, fine linear branching). Breast ultrasound for mass lesions. Breast MRI for extent assessment and contralateral evaluation (higher sensitivity but lower specificity). Stereotactic or vacuum-assisted core needle biopsy under mammographic guidance for tissue diagnosis. ER/PR receptor status, HER2, and nuclear grade (low/intermediate/high) are reported. Van Nuys Prognostic Index (VNPI) and genomic tests (Oncotype DX DCIS score) assess local recurrence risk.

Breast-conserving surgery (lumpectomy) plus adjuvant whole-breast radiotherapy (WBI, 40-50 Gy in 15-25 fractions) or accelerated partial breast irradiation (APBI) is the standard of care for most DCIS. Mastectomy for extensive disease, multicentric DCIS, or BRCA1/2 carriers. Endocrine therapy: tamoxifen 5 years (pre/postmenopausal) or aromatase inhibitor (postmenopausal) for ER-positive DCIS — reduces ipsilateral and contralateral breast events by approximately 40-50%. Active surveillance (COMET, LORD trials) is under investigation for low-risk low-grade ER-positive DCIS.

After lumpectomy plus radiotherapy: 10-year local recurrence risk approximately 10-15%; approximately half of recurrences are invasive cancer. After mastectomy: local recurrence under 1%. Disease-specific survival exceeds 98% at 10 years — DCIS has an excellent prognosis when appropriately treated. Low-grade ER-positive DCIS has very low invasive progression risk. High-grade DCIS with comedonecrosis carries higher progression risk to invasive cancer.