Uterus and endometrium -
This article was last reviewed and updated on March 6, 2019
by Emily Goebel, MD FRCPC
An endometrial polyp is a non-cancerous growth that starts from the endometrium, the tissue that lines the inside of the uterus.
Endometrial polyps are usually caused by conditions that result in high levels of estrogen such as high blood pressure, obesity, late menopause, and tamoxifen treatment.
The normal 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 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.
Serosa – The serosa is a thin layer of tissue that surrounds the outside of the uterus.
What is an endometrial polyp?
An endometrial polyp is a non-cancerous (benign) growth that sticks out from the inner surface of the endometrium. The polyp is made up of an increased number of otherwise normal-appearing endometrial glands and stromal tissue.
The growth and development of the normal endometrium is 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. Some common situations that can result in endometrial polyps include high blood pressure, obesity, late menopause, and tamoxifen treatment.
The most common symptom associated with endometrial polyps is post-menopausal or abnormal vaginal bleeding. Some patients will not experience any symptoms and the endometrial polyp will be discovered during a medical procedure for another condition.
In patients with abnormal uterine 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, a 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.
Removal of an endometrial polyp is curative, however if there are features that are worrisome (such as endometrial hyperplasia or cancer), follow-up with re-sampling by endometrial biopsy or surgery will usually be suggested.
Some endometrial polyps look different when examined under the microscope. These polyps are called variants and are often given a special name which 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.
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.