Ductal carcinoma in situ and Paget disease of the nipple
- Lesion
DCIS is breast cancer still inside the ducts, usually found as calcifications on a mammogram; Paget disease is DCIS that has spread into nipple skin.
What it is
Ductal carcinoma in situ is a clonal proliferation of malignant cells confined within ducts and lobules by an intact myoepithelial layer and basement membrane. It cannot metastasise while it stays in situ, but it is a precursor of invasive carcinoma, with a risk that depends on grade and extent. Most DCIS is found on screening mammography as calcifications. Paget disease of the nipple occurs when malignant cells from DCIS spread through the lactiferous ducts into the nipple skin, producing a crusted eczema-like rash; an underlying carcinoma is almost always present.
Structure
- Comedo DCIS: ducts filled with high-grade cells around central necrotic debris that calcifies; squeezing the cut surface extrudes toothpaste-like plugs.
- Cribriform DCIS: rigid, evenly spaced round spaces like a sieve, low or intermediate grade.
- The myoepithelial layer can be shown with p63, calponin or smooth-muscle myosin heavy chain.
- Paget cells: large, pale, single or clustered within the epidermis, positive for CK7 and often HER2; negative for melanocytic markers.
Step by step
- A luminal clone acquires driver changes (low-grade pathway: 16q loss, PIK3CA; high-grade pathway: TP53, HER2 amplification).
- It fills and expands ducts but stays within the basement membrane (DCIS).
- In high-grade DCIS, central cells outgrow their supply, die and calcify.
- Some clones spread along ducts into the nipple skin (Paget disease).
- Loss of the myoepithelial barrier and invasion of the stroma turn DCIS into invasive carcinoma.
Markers
- p63, calponin (intact myoepithelium)
- ER and PR
- HER2 (often positive in high-grade DCIS and Paget disease)
Clinical notes
- Most DCIS is asymptomatic and detected by calcifications; it is a large share of screen-detected cancers.
- Treatment is excision with clear margins, often with radiation; endocrine therapy for ER-positive DCIS lowers recurrence.
- Any persistent unilateral eczema of the nipple that does not heal is biopsied to exclude Paget disease.
Test yourself
Think of the answer, then tap the question to see it.
What feature defines DCIS rather than invasive carcinoma?
The malignant cells are confined within ducts by an intact myoepithelial layer and basement membrane.
Which type of DCIS forms linear branching calcifications?
High-grade DCIS with comedo necrosis, whose necrotic centres calcify along the ducts.
What is Paget disease of the nipple?
Spread of carcinoma cells from underlying DCIS through the lactiferous ducts into the nipple epidermis, causing a scaly red lesion.
Elsewhere in DurgiPedia
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Breast Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2026).
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Representative model, for educational purposes only.