Endometrial polyp (uterus)

What is an endometrial polyp?

An endometrial polyp is a non-cancerous growth found on the inside of the uterus. The polyp sticks out from the endometrium, a thin layer of tissue that covers the inner surface of the uterus. It is made up of an increased number of otherwise normal-appearing endometrial glands and stroma.

The uterus and endometrium

The uterus is a pear-shaped hollow organ found in the female pelvis between the rectum (the end of the large bowel) and the urinary bladder. The upper part of the uterus (fundus) is attached to the fallopian tubes while the lower part is connected to the vagina through the uterine cervix.

The walls of the uterus are made up of three layers:

  • Endometrium – The endometrium is the tissue on the inner surface of the uterus. The endometrium is made up of endometrial glands lined by one layer of cells that form a barrier called the epithelium. The epithelium is surrounded by supporting tissue called the endometrial stroma.
  • Myometrium – The myometrium is the middle layer and is made up of smooth muscle which allows the uterus to change size and contract.
  • Perimetrium – The perimetrium is a thin layer of tissue that surrounds the outside of the uterus.

What causes an endometrial polyp?

The growth and development of the normal endometrium are controlled by hormones such as estrogen. High levels of estrogen can cause increased growth of the tissue in the endometrium and over time the development of an endometrial polyp. Other associated conditions include high blood pressure, obesity, late menopause, and tamoxifen treatment.

Symptoms of an endometrial polyp

The most common symptoms associated with endometrial polyps are post-menopausal or abnormal vaginal bleeding. Some patients will not experience any symptoms and the polyp will be discovered during a medical procedure for another condition.

How do pathologists make this diagnosis?

In patients with abnormal vaginal bleeding, the endometrium is usually sampled by endometrial biopsy or endometrial (uterine) curetting (scrapings of the endometrium with a spoon-shaped instrument).  The tissue sample is then examined by your pathologist under the microscope.

When viewed under the microscope, an endometrial polyp is made up of dilated endometrial glands and stroma with thick blood vessels. Very rarely, cancer will develop in an endometrial polyp. For this reason, your pathologist will examine the polyp for abnormal cells that may indicate the presence of a pre-cancerous condition called atypical endometrial hyperplasia or cancer. If any abnormal cells are seen, they will be described in your pathology report.

Types of endometrial polyps

Some endometrial polyps look different when examined under the microscope. These polyps are called variants and are often given a special name that may be included in your report.

Some common variants include:

  • Endometrial polyp with gland crowding – This is a polyp where the glands within the polyp are closer together than usual. This may require clinical follow-up and re-sampling of the endometrium to rule out a condition called endometrial hyperplasia.
  • Adenomyomatous polyp – This type contains smooth muscle cells in addition to endometrial glands and stroma. It is a benign (non-cancerous) type of polyp.
  • Mixed polyp – This type of polyp is made up of tissue from both the endometrium and a part of the cervix called the endocervix. For that reason, it has features of both an endometrial polyp and an endocervical polyp.


Most endometrial polyps can be successfully treated by surgery alone. However if your pathologist sees features that are worrisome (such as endometrial hyperplasia or cancer), your doctor may perform a procedure called a biopsy to look for changes in the tissue surrounding the polyp. For more information about treatment options, please talk to your doctor.

by Emily Goebel, MD FRCPC (updated September 20, 2021)
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