Uterine polyps, also called endometrial polyps, are common growths that form on the inner lining of the uterus (the endometrium). These growths extend into the uterine cavity. While the discovery of any uterine growth can cause worry, most uterine polyps are benign, meaning they are non-cancerous. The primary concern is understanding the small risk that a polyp could be malignant or contain abnormal cells that might become cancerous.
What Exactly Are Uterine Polyps?
Uterine polyps are composed of an overgrowth of the endometrial tissue, which consists of glandular, stromal, and vascular elements. They attach to the uterine wall either by a thin stalk (pedunculated) or by a broad base (sessile). These growths vary significantly in size, ranging from a few millimeters to several centimeters.
The growth of polyps is linked to hormonal factors, specifically the body’s response to estrogen, which causes the endometrium to thicken. Many individuals have no symptoms, and polyps are often discovered incidentally during unrelated examinations. When symptoms do occur, the most common is abnormal uterine bleeding. This can manifest as spotting between periods, unusually heavy menstrual flow, or vaginal bleeding after menopause.
Age is a significant factor, with the peak incidence occurring in people between 40 and 49 years old, around perimenopause. Other factors that increase the likelihood of developing polyps include obesity, high blood pressure, and the use of the breast cancer medication Tamoxifen. Tamoxifen has estrogen-like effects on the uterus. Although polyps can occur at any age, they are rare in individuals under 20.
Addressing the Primary Concern: Malignancy Risk
The overwhelming majority of uterine polyps are benign, and the absolute risk of a polyp being malignant is low. The prevalence of malignancy within an endometrial polyp is typically reported as less than 5%. Some extensive reviews estimate the general prevalence of a malignant endometrial polyp to be around 2.7%.
It is important to distinguish between a benign polyp, a precancerous growth, and an actual cancerous growth (carcinoma). An endometrial polyp may contain a precancerous condition called atypical hyperplasia. This involves abnormal cell overgrowth that has a higher likelihood of progressing to cancer. When a polyp is removed, a pathologist examines the tissue to confirm its nature.
The risk that a polyp contains cancer is strongly associated with menopausal status. For premenopausal individuals, the risk of a polyp being cancerous is very low, often less than 1%. This risk increases for postmenopausal individuals, especially those experiencing abnormal vaginal bleeding. In symptomatic postmenopausal women, the risk of malignancy within a polyp can rise to approximately 3.8% to 5%.
Other specific factors that increase the probability of malignancy include advanced age, polyps larger than two centimeters, and the presence of symptoms like abnormal bleeding. The risk of a cancer being exclusively confined to the polyp itself is even smaller, reported in some studies to be around 0.3%. Therefore, a tissue sample is necessary to definitively rule out any presence of cancer.
How Uterine Polyps Are Diagnosed
The diagnostic process often begins with an initial screening method to visualize the uterine cavity. This usually involves a transvaginal ultrasound, where a slender device is placed into the vagina to create images of the uterus using sound waves. This imaging can reveal a thickened endometrium, suggesting the presence of a polyp or other growth.
To improve the clarity of the ultrasound, a procedure called sonohysterography may be performed. This involves injecting sterile saline solution into the uterus through a thin catheter. The fluid gently expands the uterine cavity, allowing for a clearer view of any growths and helping to characterize the polyp’s size and attachment point.
The definitive diagnostic tool is hysteroscopy, which is considered the gold standard for both diagnosis and treatment. A thin, lighted instrument (hysteroscope) is inserted through the vagina and cervix, allowing the healthcare provider to directly visualize the inside of the uterus. During this procedure, the provider can perform an endometrial biopsy, taking a tissue sample from the polyp or the uterine lining. This tissue is sent for pathological examination to determine its exact nature.
Treatment and Monitoring Strategies
The management of uterine polyps depends on several factors, including symptoms, menopausal status, and whether the polyp is causing issues like infertility. For small, asymptomatic polyps, particularly in premenopausal individuals, a strategy of watchful waiting may be chosen. In some cases, these polyps may resolve on their own without intervention.
Removal is often recommended, primarily to alleviate symptoms such as irregular or heavy bleeding, and to ensure that malignancy is ruled out. The most common and effective method is hysteroscopic polypectomy, which is typically a minimally invasive, outpatient procedure. Instruments passed through the hysteroscope are used to precisely remove the polyp from the uterine wall.
While some hormonal medications may be used to temporarily manage symptoms like abnormal bleeding by regulating hormone levels, these are generally short-term solutions. The symptoms often return once the medication is stopped, and the medications do not remove the polyp itself. After a polyp is removed, the tissue is always sent for pathological analysis to confirm the benign status and guide any necessary post-treatment follow-up.