Can Tamoxifen or Hormone Therapy Cause Uterine Polyps?

Yes, tamoxifen and certain types of hormone replacement therapy (HRT) that contain estrogen are associated with an increased risk of developing endometrial (uterine) polyps ^[1][2]. However, you should never stop taking a medication prescribed for cancer treatment, such as tamoxifen, on your own.

What this means for you:

• Most polyps are benign (non-cancerous): Having a polyp does not automatically mean you have cancer ^[1][3].
• Symptoms matter: Any spotting or bleeding, especially after menopause (postmenopausal bleeding), should be evaluated promptly ^[4][5].
• Teamwork is key: Do not stop your medication. Your gynecologist and your oncology or prescribing team will work together to decide the best next steps.

Why Bleeding Requires Timely Evaluation

If you are taking tamoxifen or HRT, pay close attention to any unusual bleeding ^[5]. Abnormal uterine bleeding—which includes spotting between periods, heavier than normal periods, or even a single episode of spotting after menopause—is a warning sign that requires timely medical assessment ^[4].

While bleeding is a common symptom of a simple, benign polyp, it can also be a sign of atypical hyperplasia (an abnormal overgrowth of cells that can precede cancer) or endometrial cancer ^[4][6]. Because tamoxifen use is associated with a slightly higher risk of these conditions, new bleeding should never be ignored ^[5][2].

(Note: Seek urgent medical care if you experience heavy bleeding that soaks through a pad in an hour, bleeding accompanied by severe dizziness, fainting, severe weakness, or severe pelvic pain.)

How Tamoxifen and Hormone Therapy Affect the Uterus

To understand why these medications are linked to polyps, it helps to know how they interact with the endometrium, the inner lining of the uterus. The endometrium naturally thickens in response to the hormone estrogen ^[7][8].

• Tamoxifen: Tamoxifen is a selective estrogen-receptor modulator (SERM) commonly used to treat hormone-receptor-positive breast cancer. It works by blocking estrogen in breast tissue. However, in the uterus, tamoxifen acts like estrogen (it is an “agonist”) ^[7]. This means it can stimulate the uterine lining, leading to thickening, the formation of polyps, or sometimes hyperplasia ^[2][9].
• Hormone Replacement Therapy (HRT): The effect of HRT depends on the type. Systemic estrogen-only therapy stimulates the uterine lining, which is why a progestogen is usually added (combined HRT) to protect the uterus if you have not had a hysterectomy ^[8]. Low-dose vaginal estrogen has much less effect on the rest of the body. If you have a history of breast cancer, systemic HRT is generally not recommended routinely and requires an individualized discussion with your oncology team ^[10].

Developing a Polyp vs. Having a Malignant Polyp

It is very common to feel anxious if you develop a polyp while on these medications. However, it is important to distinguish the risk of developing a polyp from the risk that a polyp contains precancerous or cancerous tissue.

While tamoxifen and estrogen therapies increase the likelihood that a polyp will form, the vast majority of these polyps are benign ^[1][3]. In pooled studies of women with endometrial polyps, estimates suggest only about 2% to 5% of polyps are malignant ^[3].

Keep in mind that this statistic is an average across study populations, not your personal risk calculator. Your individual risk of a polyp being precancerous or cancerous is generally higher if you are postmenopausal, if the polyp is large, or if you are experiencing abnormal uterine bleeding ^[11][3][12].

What Evaluation Might Involve

How a uterine polyp is handled depends heavily on your symptoms, your menopausal status, and your ultrasound findings.

• Office Biopsy and Ultrasound: Your doctor may start with a transvaginal ultrasound or an office endometrial biopsy (a small sample of the lining) to evaluate the cause of bleeding ^[13].
• Hysteroscopy: If a polyp is suspected, a traditional “blind” sampling procedure (like a basic D&C without a camera) may miss the focal polyp ^[14][15]. Instead, guidelines often recommend a hysteroscopy ^[14][16]. During this procedure, a thin, lighted camera is inserted into the uterus to see the polyp directly and remove it completely (polypectomy).
• Pathology: Any tissue that is removed must be sent to pathology (microscopic examination in a lab) to determine definitively whether it is benign, precancerous, or cancerous ^[16][17].
• Asymptomatic Patients: If you are taking tamoxifen, have no bleeding, and have not gone through menopause, routine ultrasound screening is generally not recommended ^[5][18]. Tamoxifen frequently makes the uterine lining look thick on an ultrasound even when healthy, which can lead to overdiagnosis, anxiety, and invasive procedures you do not actually need ^[5][6]. If an incidental, asymptomatic polyp is found, your doctor will discuss whether it can be safely observed or if it should be removed based on your specific risk factors ^[16][19].

Coordinating Your Care

Discovering a uterine polyp while taking tamoxifen or hormone therapy requires a team approach. Contact your prescribing doctor (such as your oncologist) and your gynecologist. They will work together to evaluate the polyp safely, determine what testing is required, and decide if any medication changes are necessary moving forward ^[5][10].