Endometrial polyp is a benign focal endometrial lesion composed of endometrial glands, stroma, and blood vessels, found as an intraluminal mass in the endometrial cavity. It occurs in 7.8-34.9% of reproductive-age women and 12-42% of postmenopausal women. Abnormal uterine bleeding (menorrhagia, intermenstrual bleeding, postmenopausal bleeding) is the most common clinical presentation. Its relationship with infertility has been proven — through mechanical obstruction and impaired endometrial receptivity. On US, it appears as focal endometrial thickening or an echogenic/isoechoic mass in the endometrial cavity — demonstrating the feeding vessel (feeder vessel) on Doppler has high specificity for diagnosis. SIS (saline infusion sonohysterography) is the gold standard US method for polyp diagnosis — intracavitary mass clearly visualized surrounded by saline. On MRI, polyp shows intermediate-high T2 signal — distinctly different from T2 hypointense leiomyoma. Risk of malignant transformation is low (0.5-4.8%) but size, symptom presence, and postmenopausal status increase risk. Hysteroscopic polypectomy is the gold standard treatment — diagnostic and therapeutic, minimally invasive, fertility preserving.
Age Range
30-70
Peak Age
50
Gender
Female predominant
Prevalence
Very Common
Endometrial polyp develops from focal, excessive proliferation of glandular and stromal cells of the endometrial basal layer. Unlike normal endometrium, polyp tissue does not regress synchronously with the menstrual cycle — basal layer cells are estrogen-sensitive but relatively resistant to progesterone, this hormonal asymmetry leads to uncontrolled growth. The polyp body consists of three main components: (1) Endometrial glands — generally dilated, cystic (microcystic pattern), irregular morphology different from functional endometrium, (2) Fibrous stroma — thickened connective tissue with dense collagen, (3) Thick-walled blood vessels — feeding artery (feeder vessel) coursing at the polyp base/stalk is characteristic. Pathophysiological basis of imaging findings: The feeding vessel originates from the endometrial basal layer and enters the polyp body — detected as a single arterial vascular structure on Doppler (specificity >95%). On US, the polyp generally appears isoechoic-hyperechoic relative to endometrium due to stromal composition. Cystic glandular dilations manifest as small anechoic foci on US and hyperintense areas on MR T2 — these cystic areas are common in polyps and serve as diagnostic clues. Intermediate-high signal on T2 reflects the mixture of fibrous stroma + glandular structures — distinctly different from the T2 hypointensity (fibrous-muscle) of leiomyoma. While malignant transformation risk is low, it increases with size >15 mm, postmenopausal status, tamoxifen use, and symptomatic polyps.
Single feeding arterial structure originating from the endometrial basal layer at polyp stalk/base on color or Power Doppler — most specific finding for endometrial polyp diagnosis (specificity >95%). In submucosal myoma, feeding artery originates from myometrium and shows peripheral circumferential pattern — this difference is the basis of Doppler differentiation between the two lesions.
Focal isoechoic or mildly hyperechoic mass in the endometrial cavity — expands the endometrial stripe or creates asymmetric thickening. Small anechoic cystic areas (dilated glands) within are common and serve as important diagnostic clues. Smooth-bordered, oval or lobulated shape. Some polyps may be completely anechoic (cystic polyp). May be hidden by being isoechoic with endometrial tissue in secretory phase — US is more diagnostic in proliferative phase (early post-menstruation). Polyp may cause erroneous measurements by creating focal thickening in endometrial thickness assessments.
Report Sentence
A ___ x ___ mm smooth-bordered, isoechoic/mildly hyperechoic focal lesion is seen in the endometrial cavity with small cystic areas within; consistent with endometrial polyp.
Single feeding arterial structure originating from endometrial basal layer at polyp stalk/base on color Doppler (feeder vessel sign) — most specific Doppler finding for polyp diagnosis (specificity >95%, sensitivity 75-80%). Vascularity within polyp body is generally minimal or absent. Feeding artery enters at polyp base and can be traced through the body. Different from peripheral circumferential pattern of submucosal myoma — vessels along pseudocapsule in myoma, single central artery in polyp.
Report Sentence
A single feeding arterial structure (feeder vessel sign) is detected at the base of the endometrial lesion on color Doppler, supporting the diagnosis of endometrial polyp.
Echogenic intracavitary mass surrounded by saline fluid on SIS — smooth surface, covered with endometrium. Polyp size, location, and stalk are precisely evaluated. No intramural component (different from submucosal myoma). Small polyps (<5 mm) may not be detected without SIS. SIS has sensitivity 93-95% and specificity 90-94% for polyp diagnosis — high correlation with hysteroscopy.
Report Sentence
On SIS, a ___ x ___ mm smooth-surfaced, echogenic intracavitary mass surrounded by saline fluid is seen in the endometrial cavity, consistent with endometrial polyp.
Intracavitary mass showing intermediate-high signal in endometrial cavity on T2W — similar or slightly lower signal than surrounding endometrium. Sharply different from marked T2 hypointensity of leiomyoma — this distinction is the most valuable MRI finding. Cystic glandular dilations appear as hyperintense dots on T2. Polyp stalk/base may show lower signal on T2 (fibrous component). Smooth-bordered, conforming to endometrial cavity. Cavity fluid may be seen as thin hyperintense ring around polyp.
Report Sentence
A ___ x ___ mm smooth-bordered intracavitary lesion showing intermediate-high signal with small hyperintense cystic areas within is seen in the endometrial cavity on T2W; consistent with endometrial polyp.
Polyp shows prominent enhancement on contrast MRI — especially in fibrous core/stalk region. Enhancement begins from vascular structures in early phase, fibrous stroma retains contrast in delayed phase. Enhancement pattern is more prominent than endometrium. Polyp generally does not show significant diffusion restriction on DWI (benign) — DWI is critical for differentiation from endometrial carcinoma.
Report Sentence
The lesion in the endometrial cavity shows prominent enhancement on contrast-enhanced series with contrast retention in the fibrous core; consistent with endometrial polyp.
Criteria
Glands responsive to hormonal stimulation, proliferative or secretory endometrium-like structure
Distinct Features
Most common type in reproductive age. Partially changes with menstrual cycle. Cyclic echogenicity change on US. Lowest malignant transformation risk. Small polyps may spontaneously regress.
Criteria
Atrophic glands, dense fibrous stroma, low glandular activity
Distinct Features
Common in postmenopausal women. More echogenic on US (dense fibrous stroma). Relatively lower signal on MR T2 (fibrous dominance). Higher malignant transformation risk than functional type — biopsy required.
Criteria
Associated with tamoxifen use, frequently multiple and large, prominent cystic glandular dilations
Distinct Features
In 20-36% of tamoxifen users. Frequently multiple, large, prominent cystic dilations. 'Swiss cheese' pattern on US (numerous cystic areas). Increased malignant transformation risk (3-10%). Hysteroscopic polypectomy + biopsy mandatory.
Distinguishing Feature
Submucosal myoma shows marked T2 hypointensity (fibrous-muscle structure), polyp shows intermediate-high T2 signal. Pseudocapsule present in myoma, absent in polyp. Feeding artery from myometrium (peripheral pattern) in myoma, from endometrial basal layer (single central artery) in polyp. Myometrial component present in myoma, absent in polyp.
Distinguishing Feature
Endometrial carcinoma shows marked diffusion restriction (low ADC), irregular borders, myometrial invasion (JZ disruption), heterogeneous enhancement, endometrial thickness >15 mm in postmenopausal bleeding. Polyp shows no DWI restriction, smooth borders, no myometrial invasion, homogeneous enhancement.
Distinguishing Feature
Endometrial hyperplasia shows diffuse endometrial thickening (not focal mass), no intracavitary mass on SIS, no single feeding artery on Doppler. Polyp shows focal mass, intracavitary lesion on SIS, positive feeder vessel sign.
Distinguishing Feature
Gestational trophoblastic disease shows positive β-hCG, 'snowstorm' US pattern (numerous small cystic areas), hypervascularity, lesion diffusely filling endometrial cavity. Polyp shows negative β-hCG, focal mass, normal vascularity, single feeder vessel.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
6-monthEndometrial polyp is the most common benign intracavitary lesion. Malignant transformation risk is low (0.5-4.8%) but increased in the presence of risk factors: postmenopausal status, size >15 mm, symptomatic polyp, tamoxifen use, Lynch syndrome. Hysteroscopic polypectomy is the gold standard treatment — both diagnostic (histopathology) and therapeutic. Expectant management (25% spontaneous regression) is an option for small (<10 mm), asymptomatic, premenopausal polyps. Every polyp detected in postmenopausal bleeding requires histopathological evaluation — 30-40% of carcinomas develop within polyps. Polypectomy improves implantation rate in infertility patients (polypectomy before IVF is recommended). Annual US screening is recommended in breast cancer patients on tamoxifen. Recurrence rate after polypectomy is 10-15% — hormonal therapy (LNG-IUD) reduces recurrence.
Endometrial polyps are usually benign but malignancy risk increases in the postmenopausal period. Hysteroscopic polypectomy is the standard treatment for symptomatic polyps. Asymptomatic small polyps can be followed. Tamoxifen users have a high polyp incidence and require careful follow-up.