Large Uterine Polyp on Ultrasound.

This video shows Uterine polyps, Ultrasound findings.
Overgrowth of cells in the lining of the uterus (endometrium) leads to the formation of uterine polyps, also known as Endometrial polyps. Endometrial polyps are a common cause of abnormal uterine bleeding.
Normally, women naturally expel these endometrial cells during menstruation. In some women, however, the growth of cells becomes excessive, resulting in either flat or protruding growths, called endometrial polyps, or in a thickening of the endometrium, called endometrial hyperplasia.
Women with atypical hyperplasia in a polyp were slightly more likely to have hyperplasia in the surrounding endometrium than those with complex hyperplasia. Conclusions: Our study illustrates that the risk of endometrial hyperplasia in a polyp concurrently involving nonpolypoid endometrium is significant.
The exact reason that polyps form is unknown, but swings in hormone levels may be a factor. Estrogen, which plays a role in causing the endometrium to thicken each month, also appears to be linked to the growth of uterine polyps.
Endometrial Hyperplasia: A condition in which the lining of the uterus grows too thick. Endometrial Intraepithelial Neoplasia (EIN): A precancerous condition in which areas of the lining of the uterus grow too thick.
It is rare for uterine polyps to be cancerous. If they aren't causing problems, monitoring the polyps over time is a reasonable approach. If you develop symptoms, such as abnormal bleeding, however, then the polyps should be removed and evaluated to confirm that there is no evidence of cancer.
Uterine polyps range in size from a few millimeters — no larger than a sesame seed — to several centimeters — golf-ball-size or larger. They attach to the uterine wall by a large base or a thin stalk.
The size of polyps may be relevant, and those above 15 mm are thought more like to lead to malignant transformation. However, this is controversial and others Gregoriou et al.69 have found no link between the size of polyps, hypertension, abnormal uterine bleeding, and malignant transformation.
Endometrial polyps are benign nodular protrusions of the endometrial surface, and one of the entities included in a differential of endometrial thickening. Endometrial polyps can either be sessile or pedunculated. They can often be suggested on ultrasound or MRI studies but may require sonohysterography or direct visualization for confirmation. Classically, endometrial hyperplasia affects the entire endometrium and results in the widening of the endometrium.
In some women, however, the growth of cells becomes excessive, resulting in either flat or protruding growths, called endometrial polyps, or in a thickening of the endometrium, called endometrial hyperplasia. Hyperplasia can lead to cancer if not treated.
Uterine polyps are more likely to develop in women who are between 40 and 50 years old than in younger women. Uterine polyps can occur after menopause but rarely occur in women under 20 years old.
The prevalence of endometrial polyps increases with age. Endometrial polyps are frequently seen in patients receiving tamoxifen. Other risk factors include foreign bodies, multiparity, chronic cervicitis, and estrogen secretion. Around 5 percent of uterine polyps are cancerous or precancerous.
Most polyps are asymptomatic although they can be a common cause of postmenopausal bleeding (can account for approximately 30% of cases 5). In pre-menopausal women, they may cause intermenstrual bleeding, metrorrhagia, and infertility. Uterine polyps range in size from a few millimeters — no larger than a sesame seed — to several centimeters — golf-ball-size or larger. They attach to the uterine wall by a large base or a thin stalk. You can have one or many uterine polyps.
The main difference between fibroids and polyps is the tissue they are made of. As mentioned earlier, fibroids are made of connective fibrous tissue, whereas polyps are made up of the same tissue that makes up the uterine lining, also known as endometrial tissue.

Signs and symptoms of uterine polyps include:
Irregular menstrual bleeding — for example, having frequent, unpredictable periods of variable length and heaviness.
Bleeding between menstrual periods.
Excessively heavy menstrual periods.
Vaginal bleeding after menopause.
Infertility.
Causes of Uterine Polyps
Each month, estrogen levels in women rise and fall, causing the lining of the uterus to thicken and then shed during your period. Polyps form when too much of that lining grows. That may be due to the changes in estrogen levels that happen just before and during menopause.
Treatment may not be necessary if the polyps do not cause any symptoms. However, polyps should be treated if they cause heavy bleeding during menstrual periods, or if they are suspected to be precancerous or cancerous. If a polyp is discovered after menopause, it should be removed.