Endometrial Polyp

Etiology

Endometrial polyps are localized overgrowths of endometrial glands, stroma, and blood vessels that project from the endometrial surface into the uterine cavity. Although the precise cause remains unknown, several well-established risk factors contribute to their development, including increasing age, hypertension, obesity, and tamoxifen therapy. Because polyp formation is closely associated with endometrial hyperplasia, exposure to unopposed estrogen is considered a major etiologic driver and is frequently implicated in both premenopausal and postmenopausal populations.

Additional proposed mechanisms include increased endometrial aromatase activity, dysregulation of growth factors, eg, transforming growth factor-β (TGF-β) and vascular endothelial growth factor (VEGF), and overexpression of the anti-apoptotic protein B-cell lymphoma-2 (BCL-2). Genetic alterations have also been identified in some polyps, supporting a multifactorial pathogenesis. Endometrial abnormalities, including polyps, occur in approximately 20% to 35% of individuals receiving chronic tamoxifen therapy, reflecting the drug’s partial estrogen-agonist effects on the endometrium.

Although most polyps are benign, malignant transformation occurs in up to 13% of cases. Risk is influenced by age, menopausal status, and symptomatology; in postmenopausal individuals, malignancy is identified in 4.47% of symptomatic cases compared with 1.51% of asymptomatic cases. Additional risk factors for malignant transformation include individuals older than 60 years, large polyp size, postmenopausal status, symptomatic bleeding, and polycystic ovary syndrome.[3][4]

Epidemiology

Endometrial polyps occur across all age groups but are most frequently identified in individuals aged between 40 and 49 years, reflecting the hormonal milieu of the late reproductive years. Among reproductive-aged individuals presenting with abnormal uterine bleeding, the prevalence of endometrial polyps is estimated at 20% to 40%, making them one of the most common structural causes of bleeding in this population.

Autopsy studies demonstrate that approximately 10% of individuals have endometrial polyps, including many who were asymptomatic during life. The likelihood of malignant transformation varies by age and menopausal status; premenopausal individuals have a substantially lower risk compared with postmenopausal individuals, in whom the prevalence of atypia or carcinoma is higher. These epidemiologic patterns underscore the importance of risk-stratified evaluation when polyps are identified in postmenopausal patients or those with additional risk factors.[5]

Pathophysiology

Endometrial polyps arise from focal overgrowths of endometrial glands and stroma around a central vascular core, driven primarily by estrogen-mediated proliferation and reduced apoptosis. Increased local aromatase expression and overexpression of anti-apoptotic proteins (eg, BCL-2) promote persistent endometrial growth, while dysregulation of growth factors, including TGF-β and VEGF, contributes to abnormal angiogenesis within the polyp.

These lesions often exhibit monoclonal stromal proliferation, supporting a neoplastic rather than purely hyperplastic origin. Most polyps remain benign; however, atypical hyperplasia or carcinoma may develop, particularly in postmenopausal individuals or those with unopposed estrogen exposure. Common findings include abnormal uterine bleeding, infertility, or incidental detection on imaging performed for unrelated indications.[6][7] Please see StatPearls' companion resource, "Abnormal Uterine Bleeding," for further information on PALM-COEIN etiologies.

Histopathology

Endometrial polyps are epithelial proliferations composed of vascular tissue, glandular structures, fibromuscular components, and connective tissue. They are typically covered by the surface endometrial epithelium and contain a prominent, thick-walled vascular core, a characteristic microscopic feature. Polyps may be sessile, pedunculated, or prolapsing, and prolapsed lesions can demonstrate secondary changes, eg, squamous metaplasia, inflammation, or ulceration due to exposure through the cervical os.

Most polyps consist of endometrial tissue that differs from the surrounding cycling endometrium and often shows reduced responsiveness to hormonal fluctuations, contributing to persistent growth. Histologic variants include atrophic, hyperplastic, and carcinomatous forms, the latter representing progression to atypical hyperplasia or carcinoma within the polyp. Stromal monoclonality and altered expression of proteins (eg, BCL-2) support a neoplastic rather than purely hyperplastic origin in many cases.[8]

History and Physical

Clinical History

Patients with endometrial polyps frequently remain asymptomatic, and many lesions are identified incidentally during evaluation for unrelated gynecologic conditions. When symptoms develop, abnormal uterine bleeding represents the most common clinical presentation. Approximately 25% of reproductive-aged individuals undergoing evaluation for abnormal uterine bleeding receive a diagnosis of endometrial polyps. Less common manifestations include pelvic pain, abdominal pain, and infertility.

Evaluation of abnormal uterine bleeding requires careful assessment of the underlying etiology, symptom severity, associated clinical features, and existing comorbidities. Please see StatPearls' companion resource, "Abnormal Uterine Bleeding," for further information. No specific bleeding pattern definitively identifies endometrial polyps; however, menorrhagia and intermenstrual spotting rank among the most frequently reported presentations. A thorough medical and surgical history remains essential for excluding alternative causes of bleeding, including coagulopathies, thyroid disorders, and structural uterine abnormalities.

Tamoxifen, a medication widely used in the treatment of breast cancer, exhibits both estrogen-agonist and estrogen-antagonist properties. Although antiestrogenic within breast tissue, tamoxifen exerts estrogenic effects on the endometrium, increasing the risk of endometrial pathology. Chronic use is associated with a 20% to 35% incidence of endometrial polyp formation. Hormone replacement therapy used to manage menopausal symptoms has also been linked to the development of endometrial polyps and commonly presents with irregular bleeding accompanied by increased endometrial thickness on ultrasonography. Please see StatPearls' companion resource, "Hormone Replacement Therapy," for further information.

Physical Examination 

Physical examination should include a general assessment, a bimanual pelvic examination, and a sterile speculum examination. Careful evaluation of the cervix and vaginal vault helps exclude other structural sources of bleeding. In some patients, a pedunculated endometrial polyp extends through the external cervical os, permitting direct visualization during examination.[9][10]

Evaluation

Transvaginal ultrasound (TVUS) is the most commonly used and widely available imaging modality for evaluating suspected endometrial polyps (see Image. Endometrial Polyp). Typical findings include focal or diffuse echogenic endometrial thickening or a well-circumscribed intracavitary lesion. In individuals with postmenopausal bleeding, an endometrial thickness less than 4 mm is strongly associated with atrophy, whereas a thickness of greater than 4 mm raises concern for endometrial pathology, including polyps. Polyp size, number, and location do not reliably correlate with symptom severity.

Saline infusion sonography (SIS) is a valuable adjunct when TVUS findings are inconclusive. During SIS, 5 to 30 mL of warmed saline is instilled into the uterine cavity to enhance visualization of intracavitary structures (see Image. Saline Infusion Sonogram). This technique improves delineation of the endometrial cavity, facilitates distinction between endometrial polyps (arising from the endometrium) and submucosal fibroids (arising beneath the endometrium), and provides superior assessment of the cornua and adnexa. Contraindications include pregnancy and active cervical or uterine infection.

Additional diagnostic tools include hysterosalpingography and hysteroscopy. Hysteroscopy offers direct visualization and is considered the gold standard for diagnosis; however, it does not provide a tissue diagnosis unless combined with biopsy or polypectomy. Because of the potential risk of premalignant or malignant pathology, histologic sampling is recommended when polyps are identified, particularly in postmenopausal individuals or those with risk factors.

Tissue diagnosis may be obtained via endometrial biopsy, dilation and curettage (D&C), or hysteroscopic polypectomy. Blind sampling with biopsy or D&C has limited sensitivity for focal lesions and should be reserved for situations in which hysteroscopic evaluation is unavailable. Laboratory studies may include a urine pregnancy test, complete blood count, and coagulation profile to assess for pregnancy, anemia, or bleeding disorders. These tests support a comprehensive evaluation but do not directly diagnose polyps.[11][12][13][14]

Treatment / Management

Conservative management with observation represents an acceptable approach for asymptomatic individuals with a low risk of malignancy. Spontaneous regression occurs in some cases; one study reported resolution of 29% of endometrial polyps within 1 year among premenopausal individuals. Conservative management generally involves periodic monitoring with transvaginal ultrasound to assess for persistence, regression, or progression of lesions. Hormonal therapy has limited supporting evidence and lacks endorsement from major clinical guidelines as a routine treatment option for endometrial polyps.[15][11](B2)

Hysteroscopic polypectomy remains the gold standard treatment for endometrial polyps. This procedure enables complete lesion removal under direct visualization while providing tissue for histopathologic evaluation. Because endometrial polyps may coexist with additional endometrial abnormalities, microscopic examination of both the excised polyp and the surrounding endometrium remains essential. Benign polyps have been identified in 20% of individuals diagnosed with endometrial carcinoma, highlighting the importance of comprehensive tissue assessment and pathologic review.

The optimal timing of polypectomy for asymptomatic, low-risk patients remains uncertain. A retrospective study evaluating routine polyp removal identified no malignancies in histologic specimens, suggesting that universal polypectomy may not be necessary in all cases. However, polyps measuring more than 1.5 cm demonstrate a lower likelihood of spontaneous regression. Surgical removal generally remains appropriate for symptomatic individuals and for those with risk factors associated with malignant transformation.

Hysterectomy provides a definitive surgical option by eliminating both recurrence risk and the potential for future malignant transformation. However, this approach carries substantially greater morbidity and cost than less invasive interventions and warrants consideration only after comprehensive counseling and when alternative management strategies are unsuitable. Patients who develop anemia secondary to abnormal uterine bleeding should receive iron supplementation as part of supportive management to correct iron deficiency and improve hematologic status.[7][16][17](B2)

Differential Diagnosis

Accurate differentiation relies on a combination of clinical history, imaging characteristics, and histologic evaluation, with hysteroscopy and tissue sampling providing the highest diagnostic precision.[18][19] Several gynecologic conditions can mimic the presentation or imaging appearance of endometrial polyps and must be considered during evaluation. Submucosal leiomyomas are a common alternative diagnosis; these lesions arise from the myometrium beneath the endometrium and may appear as intracavitary masses on ultrasound or hysteroscopy. Adenomyomas can also resemble polyps but typically demonstrate myometrial involvement and heterogeneous echotexture.

Retained products of conception should be considered in individuals with recent pregnancy, miscarriage, or postpartum bleeding, as they may present with irregular bleeding and intracavitary tissue. Endometrial hyperplasia and endometrial carcinoma may produce focal or diffuse endometrial thickening and require tissue sampling to exclude premalignant or malignant pathology. Finally, uterine sarcoma, although rare, should be considered when lesions are large, rapidly growing, or associated with atypical imaging features or systemic symptoms.

Staging

Endometrial polyps lack a formal staging system because they are benign, localized intracavitary lesions that neither invade the myometrium nor metastasize. Management and prognostic assessment, therefore, do not rely on a polyp-specific classification system. When atypical hyperplasia or carcinoma is identified within an endometrial polyp, staging follows the underlying endometrial carcinoma rather than the polyp itself. In these cases, clinicians apply the FIGO staging system for endometrial cancer, with stage assignment based on factors, eg, the depth of myometrial invasion, cervical involvement, extrauterine spread, and lymph node status. Although endometrial polyps are not independently staged, any malignant transformation requires evaluation and management in accordance with established endometrial carcinoma staging guidelines.[20][21]

Prognosis

Most individuals experience significant improvement in abnormal uterine bleeding following hysteroscopic polypectomy, particularly those with intermenstrual spotting or heavy menstrual bleeding. Treatment is generally effective, with low recurrence rates, especially in patients who initially present with a small number of polyps. The recurrence rate of histologically confirmed polyps is approximately 2.5% to 3.7%, reflecting the durability of hysteroscopic removal.

Recurrence may be further reduced when polypectomy is combined with endometrial ablation or placement of a levonorgestrel-releasing intrauterine device (LNG-IUD); however, evidence supporting these adjunctive strategies remains limited, and their use is largely restricted to research settings. In individuals with tamoxifen-associated polyps, the LNG-IUD has demonstrated benefit in reducing the formation of new polyps.

Fertility outcomes after hysteroscopic polypectomy are generally favorable. Several studies report improved spontaneous pregnancy and term delivery rates following removal, with outcomes appearing similar regardless of whether polyps are 1 cm or less, greater than 1 cm, or multiple. Likewise, first-trimester miscarriage rates do not differ significantly based on polyp size or number, supporting polypectomy as a beneficial intervention for patients seeking conception.[5][22][23]

Complications

All resected specimens from hysteroscopic polypectomy should be submitted for pathologic evaluation to exclude atypia or carcinoma. If malignancy is identified, referral to gynecologic oncology is recommended for comprehensive staging and management. Procedural complications are uncommon; hysteroscopic polypectomy carries a low risk of infection, bleeding, or uterine perforation, and the incidence of intrauterine adhesions is rare.

Infertility Considerations 

The relationship between endometrial polyps and infertility remains an area of active investigation. A prospective randomized controlled trial demonstrated that hysteroscopic polypectomy before intrauterine insemination significantly improves pregnancy rates, suggesting a beneficial effect on implantation. Polyps also appear more prevalent in individuals with fallopian tube obstruction compared with those with tubal patency, indicating a possible association with other infertility factors.

However, a retrospective study of patients undergoing in vitro fertilization (IVF) found no significant differences in pregnancy, miscarriage, or live birth rates among individuals with untreated polyps. Despite these mixed findings, current expert recommendations favor the removal of polyps before IVF, given the potential for improved endometrial receptivity and the low risk associated with hysteroscopic removal.[24][7][3]