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.
Endometrial polyps are frequently seen in patients receiving Tamoxifen.
Most polyps are asymptomatic although they can be a common cause of post-menopausal bleeding (can account for approximately 30% of cases 5). In menstruating women, they may cause inter-menstrual bleeding, metrorrhagia, and infertility.
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
There may be a predilection towards the fundal and cornual regions within the uterus. They can be multiple in ~20% of cases.
Although endometrial polyps may be visualized at trans-vaginal 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 color 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
Polyps are best characterized 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.
Color Doppler interrogation may show flow within the stalk.
Signal characteristics include:
- T1: often isointense signal to endometrium
- T2: endometrial polyps are often seen as low-signal-intensity intra-cavitary masses surrounded by high-signal-intensity fluid and endometrium.
- T1 C + (Gd): can show either homogeneous or heterogeneous enhancement.
Polyps may be seen as pedunculated or sessile filling defects within the uterine cavity
A very small percentage (0.5-3%) of polyps may contain endometrial carcinoma 4.
Treatment and prognosis
Most polyps are benign and may be treated with a polypectomy, if symptomatic.
Entities that can potentially mimic an endometrial polyp include:
- uterine leiomyoma(s): especially if pedunculated and sub-mucosal, although most leiomyomas tend to be hypoechoic on ultrasound have hypointense on MRI
- foci of endometrial hyperplasia
- endometrial carcinoma
For hyperechoic content within the endometrium also consider: