Endometrial hyperplasia is an abnormal proliferation of the endometrial glands and stroma, defined as diffuse smooth thickening >10 mm ¹³. One of the major concerns is the potential malignant transformation to endometrial carcinoma.

Epidemiology

Endometrial hyperplasia affects women of all age groups ¹².

Associations

Unopposed estrogen stimulation (either from an endogenous or exogenous source) is implicated in its pathogenesis; some of these conditions include:

• obesity

• polycystic ovary syndrome

• pregnancy (including ectopic pregnancy)

• estrogen-secreting ovarian tumors

  • granulosa cell tumor of the ovary

• tamoxifen 

Clinical presentation

A great majority of patients present with abnormal vaginal bleeding. 

Pathology

Hyperplasia with increased gland-to-stroma ratio; there is a spectrum of endometrial changes ranging from glandular atypia to frank neoplasia.

There are several types of endometrial hyperplasia, which include:

• simple hyperplasia without atypia also known as cystic endometrial hyperplasia

• simple hyperplasia with atypia 

• complex hyperplasia without atypia 

• complex hyperplasia with atypia 

Hyperplasia can be also classified into two broad groups ⁵:

• hyperplasia without cellular atypia

• hyperplasia with cellular atypia

Radiographic features

Ultrasound

Imaging the endometrium on days 5-10 of a woman's cycle reduces the variability in endometrial thickness.

• premenopausal

  • normal endometrial thickness depends on the stage of the menstrual cycle, but a thickness of 15 mm is considered the upper limit of normal in the secretory phase

  • hyperplasia can be reliably excluded in patients only when the endometrium measures less than 8 mm ¹⁵

• postmenopausal

  • a thickness of >5 mm is considered abnormal

The appearance can be non-specific and cannot reliably allow differentiation between hyperplasia and carcinoma ⁵. Usually, there is a homogeneous smooth increase in endometrial thickness, but endometrial hyperplasia may also cause asymmetric/focal thickening with surface irregularity, an appearance that is suspicious for carcinoma. Cystic changes can also be seen in endometrial hyperplasia.

Ultrasound features that are suggestive of endometrial carcinoma as opposed to hyperplasia include ¹³:

• heterogeneous and irregular endometrial thickening

• polypoid mass lesion

• intrauterine fluid collection

• frank myometrial invasion

MRI

• T2: hyperplasia is often isointense to hypointense to normal endometrium ⁷

Treatment and prognosis

Up to one-third of endometrial carcinoma is believed to be preceded by endometrial hyperplasia, therefore a biopsy is required for a definitive diagnosis.

Because endometrial hyperplasia has a non-specific appearance, any focal abnormality should lead to biopsy if there is clinical suspicion for malignancy (e.g. vaginal bleeding).

Differential diagnosis

On ultrasound, appearances can potentially simulate:

• normal thickening during the secretory phase: see endometrial thickness

• sessile endometrial polyp(s): may contain cystic spaces ⁴

• submucosal uterine fibroids

• endometrial cancer

• adherent intrauterine blood clot

• pregnancy (including ectopic pregnancy)

• incomplete abortion ¹⁴

See also

• abnormal thickening of the endometrium