[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Female genital tract](https://durgical.com/en/general-pathology/areas/female-genital/) › Endometrial polyps and hyperplasia

# 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.

Updated Nov 12, 2026

## Key points

- Sources of unopposed estrogen: anovulation, polycystic ovary syndrome, obesity (aromatase in fat), estrogen-only therapy, estrogen-secreting ovarian tumours (granulosa cell tumour).
- Hyperplasia without atypia: crowded, irregular, sometimes cystic glands with normal nuclei; low risk of carcinoma.
- Atypical hyperplasia (EIN): crowded back-to-back glands with nuclear atypia (round, vesicular nuclei, nucleoli) that differ from the background; high risk, and carcinoma is often found at hysterectomy.
- PTEN loss is an early event shared with endometrioid carcinoma; Cowden syndrome raises the risk.
- Polyps: dense stroma, thick-walled vessels, dilated glands; associated with tamoxifen; clonal stromal rearrangements (6p21).

## 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](https://durgical.com/en/conditions/endometrial-hyperplasia/) | Excess glands, normal nuclei | Low | Progestins, treat the estrogen source |
| [Atypical hyperplasia (EIN)](https://durgical.com/en/conditions/endometrial-hyperplasia/) | 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.

## Memory aid

Atypia is the alarm: hyperplasia without it is noise from estrogen; with it, cancer is knocking or already inside.

## 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.

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## Elsewhere in DurgiPedia

- [Aromatase (CYP19A1)](https://durgical.com/en/biochemistry/enzymes/aromatase/)
- [Actions of estrogen and progesterone](https://durgical.com/en/physiology/actions-of-estrogen-and-progesterone/)

## Connections

## Related 8

- [Endometrium and abnormal uterine bleeding](https://durgical.com/en/general-pathology/endometrium-and-abnormal-uterine-bleeding/)
- [Endometrioid endometrial carcinoma](https://durgical.com/en/general-pathology/endometrioid-endometrial-carcinoma/)
- [Endometrial carcinoma: types and molecular groups](https://durgical.com/en/general-pathology/endometrial-carcinoma-types-and-molecular-groups/)
- [Granulosa cell tumours: adult and juvenile](https://durgical.com/en/general-pathology/granulosa-cell-tumours-adult-and-juvenile/)
- [Non-neoplastic ovarian cysts and polycystic ovaries](https://durgical.com/en/general-pathology/non-neoplastic-ovarian-cysts-and-polycystic-ovaries/)
- [Hyperplasia: physiologic and pathologic](https://durgical.com/en/general-pathology/hyperplasia-physiologic-and-pathologic/)
- [Precancerous conditions: when chronic inflammation, metaplasia or hyperplasia raise the risk](https://durgical.com/en/general-pathology/precancerous-conditions-when-chronic-inflammation-metaplasia-or-hyperplasia-rais/)
- [Obesity: leptin, adipokines and its consequences](https://durgical.com/en/general-pathology/obesity-leptin-adipokines-and-its-consequences/)

## Related conditions 7

- [Endometrial hyperplasia](https://durgical.com/en/conditions/endometrial-hyperplasia/)
- [Endometrial cancer](https://durgical.com/en/conditions/endometrial-cancer/)
- [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/)
- [Polycystic ovary syndrome](https://durgical.com/en/conditions/polycystic-ovary-syndrome/)
- [Obesity](https://durgical.com/en/conditions/obesity/)
- [Breast cancer](https://durgical.com/en/conditions/breast-cancer/)
- [Menopause and climacteric syndrome](https://durgical.com/en/conditions/menopause-and-climacteric-syndrome/)

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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: [Abnormal Uterine Bleeding](https://www.ncbi.nlm.nih.gov/books/NBK532913/) (StatPearls (NCBI Bookshelf), 2026); [Endometrial Cancer](https://www.ncbi.nlm.nih.gov/books/NBK525981/) (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/endometrial-polyps-and-hyperplasia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/endometrial-polyps-and-hyperplasia/