Proliferative breast disease without atypia
- Lesion
Benign growths of breast cells that are crowded but not abnormal; they slightly raise cancer risk and some can look like cancer on a mammogram.
What it is
Proliferative breast disease without atypia includes benign lesions in which epithelial cells multiply but remain varied and normal-looking. Usual ductal hyperplasia fills ducts with a mixed population of cells, sclerosing adenosis and radial scars compress glands within fibrous stroma in ways that mimic invasive carcinoma, and intraductal papillomas grow on fibrovascular cores within ducts. All keep their myoepithelial layer, which is the key to telling them from cancer, and they raise the risk of later breast cancer only slightly.
Structure
- Usual ductal hyperplasia: ducts partly or completely filled by overlapping cells of varying size and orientation.
- Sclerosing adenosis: lobular architecture preserved at low power, with crowded small glands squeezed into cords.
- Radial scar: hyalinised centre with distorted ducts; may contain papilloma or other changes.
- Papilloma: a soft mass within a dilated duct, sometimes with infarction causing bleeding.
Step by step
- Hormonal stimulation drives proliferation of the terminal duct lobular unit and ducts.
- Cells multiply but remain polyclonal or minimally clonal, retaining varied differentiation.
- Stromal proliferation and sclerosis can trap and distort glands (adenosis, radial scar).
- Because the background proliferation is increased, the lifetime risk of cancer rises slightly in both breasts.
Markers
- p63, calponin and smooth-muscle myosin heavy chain (myoepithelial cells)
- CK5/6 mosaic pattern (usual hyperplasia)
- ER heterogeneous
Clinical notes
- Most are found on mammography or as small lumps; a papilloma presents with nipple discharge.
- Radial scars and papillomas found on core biopsy are often excised to exclude an associated carcinoma.
Test yourself
Think of the answer, then tap the question to see it.
Why can sclerosing adenosis be mistaken for invasive carcinoma?
Its compressed small glands in dense stroma look infiltrative; the preserved myoepithelial layer shows it is benign.
What does a radial scar look like on mammography?
A stellate (spiculated) lesion that mimics carcinoma.
How much does proliferative disease without atypia raise breast cancer risk?
Slightly, about one and a half to two times the baseline risk.
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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: Fibrocystic Breast Disease (StatPearls (NCBI Bookshelf), 2026); Breast Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2026).
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Representative model, for educational purposes only.