A diagnosis of an abnormal growth in the uterus can understandably cause immediate concern about cancer. A uterine polyp, also known as an endometrial polyp, is a common growth that arises from the tissue lining the inside of the uterus. While the distinction between a benign polyp and a cancerous tumor can be confusing, these polyps are overwhelmingly non-cancerous. Understanding how these growths are classified, diagnosed, and managed can provide clarity.
Defining Uterine Polyps
Uterine polyps are localized overgrowths of the endometrium, the tissue that lines the uterine cavity. These growths are typically composed of a dense, fibrous core containing blood vessels and glands. They are common, affecting women across all age groups, with peak incidence observed between 40 and 49 years old.
Polyps vary widely in size, ranging from a few millimeters to several centimeters, and may occur as single or multiple lesions. They attach to the uterine wall either by a thin, elongated stalk (pedunculated) or by a broad, flat base (sessile).
Polyp development is influenced by hormones, particularly estrogen, which stimulates the growth of the endometrial lining. This links formation to conditions of unopposed estrogen, such as taking tamoxifen or hormone replacement therapy without progesterone. The most common symptom leading to their discovery is abnormal uterine bleeding, including heavy menstrual flow, bleeding between periods, or postmenopausal vaginal bleeding.
Classifying Abnormal Growths in the Uterus
Abnormal growths are broadly referred to as neoplasms or tumors, which are categorized based on their potential to spread and their cellular characteristics. A tumor describes any abnormal mass of tissue resulting from excessive cell division. Abnormal growths in the uterus fall into three main types: benign, pre-malignant, and malignant.
Benign growths are non-cancerous and remain localized, meaning they do not invade surrounding tissues or spread to distant parts of the body. Uterine polyps and uterine fibroids are common examples of benign tumors. Pre-malignant lesions, such as atypical endometrial hyperplasia, show abnormal cellular changes but have not yet become cancer.
Malignant tumors, or cancers, are characterized by cells that grow uncontrollably, invade adjacent tissues, and possess the ability to metastasize. Endometrial carcinoma, which begins in the uterine lining, is the most common form of uterine cancer. A uterine polyp is fundamentally a benign neoplasm, lacking the invasive and metastatic properties of a malignant one.
The Likelihood of Malignant Transformation
Although uterine polyps are benign, they carry a small, measurable risk of containing cancerous cells or undergoing malignant transformation. This risk is statistically low, with the prevalence of malignant polyps estimated to be approximately 2% to 5% overall.
The likelihood of a polyp being malignant varies significantly depending on menopausal status. The risk of cancer or pre-cancerous changes is much lower in premenopausal women (estimated at 1% to 2%). This risk rises in postmenopausal women, where the rate of pre-malignancy or malignancy typically ranges between 4.9% and 5.1%.
Certain factors further increase this minimal risk:
- Advanced age and postmenopausal status.
- The presence of abnormal uterine bleeding.
- Polyps larger than two centimeters.
- Risk factors like obesity, hypertension, or diabetes.
- The presence of multiple polyps or a history of tamoxifen use.
Diagnosis and Treatment Options
Suspicion of a uterine polyp often arises during evaluation for abnormal bleeding or routine imaging. Non-invasive techniques like transvaginal ultrasound visualize the uterine lining, often revealing thickened tissue. Sonohysterography, a more detailed imaging procedure, involves injecting saline solution into the uterus during an ultrasound to clearly outline the polyp.
The definitive method for both diagnosis and treatment is hysteroscopy, considered the gold standard procedure. During hysteroscopy, a thin, lighted telescope is inserted into the uterine cavity, providing a direct view of the polyp. The polyp is then surgically removed using instruments passed through the hysteroscope, known as hysteroscopic polypectomy.
The primary goal of removal is to resolve symptoms and obtain tissue for pathological examination. The removed polyp is sent for a biopsy, which is the only way to definitively confirm its benign status and rule out cancerous cells. While small, asymptomatic polyps may be monitored, removal is usually recommended for symptomatic polyps or those with a higher risk profile for malignancy.