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Endometrial polyp

Endometrial polyps are benign nodular protrusions of the endometrial surface, and one of the entities included in a differential of endometrial thickening. Endometrial polyps can either be sessile or pedunculated. They can often be suggested on ultrasound or MRI studies, but may require sonohysterography or direct visualization for confirmation.

Epidemiology

The prevalence of endometrial polyps increases with age, and ranges from 7.8-34.9%. Endometrial polyps are frequently seen in patients receiving Tamoxifen.

Clinical presentation

Most polyps are asymptomatic although they can be a common cause of post-menopausal bleeding (can account for approximately 30% of cases 5). In pre-menopausal women, they may cause inter-menstrual bleeding, metrorrhagia, and infertility.

Pathology

Polyps can be histologically characterized as localized hyperplastic overgrowths of glands and stroma. They consist of irregularly distributed endometrial glands and stroma and generally consist of three components: 

  • a stroma of focally or diffusely dense fibrous or smooth muscle tissue
  • thick-walled vessels
  • endometrial glands 

2-4% of "benign" polyps with have a small focus of cancer within them.

Variants
Location

There may be a predilection towards the fundal and cornual regions within the uterus. They can be multiple in ~20% of cases.

Radiographic features

Ultrasound

Although endometrial polyps may be visualised at transvaginal ultrasound as nonspecific endometrial thickening, they may also be identified as focal masses within the endometrial canal. 

  • a stalk to the polyp may either be thin or broad based
  • a feeding vessel may be seen extending to the polyp on colour Doppler imaging
  • cystic spaces corresponding to dilated glands filled with proteinaceous fluid may be seen within the polyp and is considered a relatively characteristic feature 3
  • may appear as just diffusely thickened endometrium, without visualisation of a discrete mass (mimicking endometrial hyperplasia)
  • Colour Doppler: may show flow within the stalk

3D ultrasound may be useful to help delineate the borders of a polyp.

Sonohysterography 

Although not always necessary for a diagnosis, polyps are well-characterised on sonohysterography and appear as echogenic, smooth, intra-cavitary masses outlined by fluid. The typical appearance of an endometrial polyp at sonohysterography is as a well-defined, homogeneous, polypoid lesion that is isoechoic to the endometrium with preservation of the endometrial-myometrial interface 5. There is usually a well-defined vascular pedicle within the stalk.

Pelvic MRI

Signal characteristics include:

  • T1: often isointense signal to endometrium
  • T2: endometrial polyps are often seen as hypointense intracavitary masses surrounded by hyperintense fluid and endometrium
  • T1 C+ (Gd): can show either homogeneous or heterogeneous enhancement
Hysterosalpingography (HSG)

Polyps may be seen as pedunculated or sessile filling defects within the uterine cavity. This is not a preferred method for evaluation compared with the other modalities.

Treatment and prognosis

Most polyps are benign and may be treated with a polypectomy, if symptomatic.

A very small percentage (0.5-3%) of polyps may contain endometrial carcinoma 4.

Differential diagnosis

Entities that can potentially mimic an endometrial polyp include:

For hyperechoic content within the endometrium also consider:

See also


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