Uterine fibroids are the most common masses found in the uterus on ultrasound. Fibroids are benign smooth muscle tumors that the majority of women have by the time of menopause. Fibroids can cause pain, vaginal bleeding and contribute to infertility.
Fibroids can occur throughout the uterus. Fibroids can extend from the surface of the uterus into the pelvis mimicking an ovarian or pelvic mass. They can be under a centimeter to massive occupying the entire uterus and extending into the abdomen.
Uterine cancer or leiomyosarcoma is indistinguishable from fibroids on imaging. Other uterine masses that can mimic fibroids include : endometrial cancer, focal adenomyosis, and other rare tumors of the uterus. Some of these can only be diagnosed after surgical removal.
On ultrasound, uterine fibroids most commonly look like solid masses that are darker than the uterus. They can however be the same as the uterine wall or brighter as well. Calcifications are commonly seen. Fibroids can degenerate and have cystic areas. Fibroids can bleed especially during pregnancy.
Fibroids can mimic endometrial cancer when they protrude into the endometrial cavity. They can mimic cervical cancer when they grow in the cervix. Fibroids can extend outside the uterus and mimic pelvic or ovarian masses. Fibroids can mimic uterine cancer. This is indistinguishable on imaging.
Complications of fibroids are not common but important. They can rarely degenerate into cancer or leiomyosarcoma. Fibroids which are attached by a stalk to the uterus can twist on themselves and become infarcted. This needs to be diagnosed and treated promptly to prevent complications like peritonitis and bleeding. Fibroids can rarely become infected. Fibroids can rarely spread to other parts of the body. Pregnancy can cause fibroids to grow.
Fibroids can be treated surgically by removing the fibroids individually or removing the the entire uterus. Hormone administration and uterine artery embolization are some less invasive options. Uterine artery embolization treats fibroids by occluding their arteries supply. This is done by a specially trained interventional radiologist.
Uterine fibroids on ultrasound are common and have a variety of appearances. Most uterine masses are fibroids although other possibilities such as cancer always needs to be considered. The appearance of fibroids and uterine cancer overlaps. Complications are rare but important to diagnose promptly.