Endometrial hyperplasia

Definition

• Endometrial hyperplasia is an abnormal proliferation of endometrial glands with an increased gland-to-stroma ratio compared with proliferative endometrium.

Classification

• WHO classification: The WHO distinguishes between hyperplasia without atypia & atypical hyperplasia/EIN.
• Cause: The cause is unopposed estrogen effect.
• Progression risk without atypia: The risk of progression for hyperplasia without atypia is at < 5% over 20 years.

• The 2014 WHO classification, retained in 2020, distinguishes two categories: hyperplasia without atypia and atypical hyperplasia or endometrial intraepithelial neoplasia (EIN), both terms being synonymous.
• The atypical form is the precursor of endometrioid adenocarcinoma; EIN is regarded as a mutationally activated, monoclonal pre-malignancy.

Aetiopathogenesis

Aetiology and risk factors

• The usual cause is oestrogen stimulation without adequate progesterone opposition.
• Risk factors are early menarche, late menopause, nulliparity, obesity, diabetes mellitus, PCOS, functional tumours such as granulosa cell tumours, and Lynch syndrome.

Clinical features

• Most women present with abnormal uterine bleeding; hyperplasia has been estimated to account for about 15% of postmenopausal bleeding.
• About 40% of women with EIN are diagnosed with endometrial carcinoma within 12 months, most likely because of a coexisting carcinoma not sampled at biopsy.

Histology

• EIN criteria are: gland area exceeding stromal area, cytology differing from the background, lesion diameter over 1 mm, and exclusion of mimics and carcinoma.

Diagnosis

Typical imaging findings

• Ultrasound: The endometrium is thickened along its whole length and heterogeneous, without a demarcable focal lesion. The border with the myometrium remains smooth and continuous; no invasion of the uterine wall.
• Ultrasound: The endometrium is uniformly thickened along the whole cavity and measures more than 20 mm between the calipers. It stays echogenic and homogeneous; the border to the myometrium is smooth and preserved throughout.

• Ultrasound may show a thickened endometrium; the diagnosis is made histologically.
• A biopsy may under-sample the lesion; hyperplasia may also be shed with menstruation or regress spontaneously.

Keep learning in the app

Further reading (selection)

1. New concepts for an old problem: the diagnosis of endometrial hyperplasia (Hum Reprod Update 2017, PubMed Central)
2. StatPearls: Endometrial Hyperplasia (NCBI Bookshelf)
3. Atypical Endometrial Hyperplasia and Concurrent Cancer: A Comprehensive Overview on a Challenging Clinical Condition (Cancers (Basel) 2024, PubMed Central)
4. DocCheck Flexikon, Endometriumhyperplasie

Cross-references