Endometrial polyps and hyperplasia
- Lesion
Too much estrogen without progesterone makes endometrial glands multiply. Without atypia the risk is low; with atypia it is close to cancer.
What it is
Endometrial polyps and hyperplasia are benign proliferations that cause abnormal bleeding, typically around and after menopause. Polyps are localized outgrowths with a clonal stroma. Hyperplasia is a diffuse increase in glands over stroma caused by prolonged estrogen without progesterone; it is divided into hyperplasia without atypia, which seldom becomes cancer, and atypical hyperplasia (endometrioid intraepithelial neoplasia), the direct precursor of endometrioid carcinoma, which often already coexists with it.
Structure
- Polyp: a sessile or pedunculated mass projecting into the cavity; glands, often dilated, in a fibrous stroma with clusters of thick-walled vessels.
- Hyperplasia without atypia: glands of varying size and shape in excess of stroma, lined by proliferative-type cells without atypia.
- Atypical hyperplasia: a focus of closely packed glands whose cells look different from the surrounding glands, with enlarged round nuclei and lost polarity; no stromal invasion.
Step by step
- Ovulation fails or estrogen comes from fat, drugs or a tumour, and is not balanced by progesterone.
- Estrogen keeps endometrial glands dividing; the gland-to-stroma ratio rises (hyperplasia without atypia).
- Under this pressure, a clone acquires PTEN loss and other mutations and grows as atypical hyperplasia.
- Further mutations (PIK3CA, ARID1A, KRAS, mismatch repair defects) allow invasion: endometrioid carcinoma.
Benign endometrial proliferations compared
| Lesion | Key microscopic feature | Cancer risk | Usual handling |
|---|---|---|---|
| Endometrial polyp | Fibrous stroma with thick-walled vessels | Low; higher after menopause and with tamoxifen | Removal by hysteroscopy |
| Hyperplasia without atypia | Excess glands, normal nuclei | Low | Progestins, treat the estrogen source |
| Atypical hyperplasia (EIN) | Crowded glands with nuclear atypia | High; carcinoma often already present | Hysterectomy, or progestins if fertility is wanted |
Clinical notes
- Present with heavy, prolonged or postmenopausal bleeding.
- Women with obesity, diabetes, polycystic ovary syndrome or on estrogen-only therapy are at higher risk.
- Tamoxifen acts as an estrogen agonist on the endometrium, so treated breast cancer patients develop polyps, hyperplasia and carcinoma more often.
Test yourself
Think of the answer, then tap the question to see it.
What is the most important feature for the cancer risk of endometrial hyperplasia?
Nuclear atypia: atypical hyperplasia is the direct precursor of endometrioid carcinoma and often coexists with it.
How does obesity cause endometrial hyperplasia?
Aromatase in adipose tissue converts androgens to estrogen, giving prolonged estrogen without progesterone.
Which breast cancer drug is linked to endometrial polyps and carcinoma?
Tamoxifen, which acts as an estrogen agonist on the endometrium.
Elsewhere in DurgiPedia
Connections
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: Abnormal Uterine Bleeding (StatPearls (NCBI Bookshelf), 2026); Endometrial Cancer (StatPearls (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.