“Fibroid cyst” is not a single medical condition. The term blends two separate growths that develop in different parts of the reproductive system: uterine fibroids and ovarian cysts. Both are common, both are almost always noncancerous, and both can cause pelvic pain, but they differ in what they’re made of, where they grow, and how they behave. Understanding which one you’re dealing with changes what happens next.
Fibroids and Cysts Are Different Growths
Uterine fibroids are solid masses made of muscle and connective tissue that grow in or around the uterus. They range from the size of a seed to the size of a grapefruit, sometimes larger. Ovarian cysts, by contrast, are fluid-filled sacs that form on or inside the ovaries. Think of it this way: a fibroid is like a dense rubber ball, and a cyst is like a water balloon.
Because they sit in different organs and have different compositions, they show up differently on imaging. An ultrasound can usually distinguish the two, which is why the first step after pelvic symptoms is almost always an ultrasound.
What Causes Each One
Most ovarian cysts form as a normal part of the menstrual cycle. Each month, a small sac called a follicle releases an egg. Sometimes the follicle doesn’t release the egg and instead fills with fluid, creating a follicular cyst. Other times the egg is released normally, but the structure left behind (the corpus luteum) fills with fluid rather than dissolving. These “functional” cysts are extremely common and typically shrink on their own within about 60 days.
Fibroids have a less straightforward origin. They develop from a single smooth muscle cell in the uterine wall that begins multiplying abnormally. Hormones, particularly estrogen and progesterone, fuel their growth, which is why fibroids tend to enlarge during the reproductive years and often shrink after menopause. Symptomatic fibroids affect up to 25% of all women, and that number climbs to 30 to 40% in the years approaching menopause. Black women are disproportionately affected, with nearly double the prevalence of other racial and ethnic groups.
Types of Fibroids by Location
Not all fibroids behave the same way, and their location determines which symptoms they cause. There are four main types:
- Intramural fibroids grow within the muscular wall of the uterus and are the most common type. They can stretch the uterus as they enlarge.
- Submucosal fibroids grow into the inner cavity of the uterus. Even small ones can cause heavy bleeding because they distort the uterine lining.
- Subserosal fibroids grow on the outer surface of the uterus and tend to cause pressure symptoms rather than bleeding, since they push against surrounding organs.
- Pedunculated fibroids are submucosal or subserosal fibroids that develop a stalk, hanging like a pendulum inside or outside the uterus.
How Symptoms Differ
Fibroids and ovarian cysts can both cause pelvic pain and discomfort during sex, which is one reason they get confused. But the pattern of symptoms tends to be distinct.
Fibroids are most closely associated with changes in menstrual bleeding. Heavy periods, prolonged periods, and bleeding between periods are hallmark signs. As fibroids grow, they can also press on the bladder (causing frequent urination or difficulty emptying it), press on the rectum, or create a persistent aching in the lower back. The symptoms tend to build gradually over months or years.
Ovarian cysts are more likely to cause bloating, a feeling of fullness or pressure in the lower abdomen, and a dull ache on one side. Many cysts cause no symptoms at all and are discovered incidentally during an unrelated ultrasound. The red flag with cysts is sudden, sharp pain, especially if accompanied by nausea, vomiting, or fever. That can signal a ruptured cyst or ovarian torsion, where the cyst causes the ovary to twist on itself, cutting off its blood supply. Torsion is a surgical emergency.
Cancer Risk Is Extremely Low
One of the most common worries with either condition is cancer. Fibroids are benign in the vast majority of cases. In a study of nearly 1,400 surgeries performed for presumed fibroids, cancerous tissue (leiomyosarcoma) was found in roughly 2 out of every 1,000 cases. In women under 40, the rate was zero. The risk increases slightly after age 49 but still remains around 1.2%.
Most ovarian cysts are also benign, particularly the functional cysts that arise from the menstrual cycle. Cysts with unusual features on imaging, such as solid components, irregular walls, or large size, get additional evaluation to rule out ovarian cancer, but the overwhelming majority turn out to be harmless.
When Treatment Is Needed
Many ovarian cysts need no treatment at all. Because functional cysts usually resolve within two months, the standard approach is to simply monitor them with a follow-up ultrasound. Surgery is typically considered when a simple cyst exceeds about 7 centimeters in premenopausal women or 5 centimeters in postmenopausal women, or when a cyst has features that raise concern on imaging.
Fibroids only require treatment when they cause symptoms that affect your quality of life, such as heavy bleeding that leads to anemia, pain that disrupts daily activities, or pressure on the bladder or bowel. Small, asymptomatic fibroids are often monitored over time without any intervention.
Treatment Options for Fibroids
When fibroids do need treatment, there are several paths depending on fibroid size, location, and whether you want to preserve fertility.
Hormonal treatments can slow fibroid growth and reduce heavy bleeding. These don’t eliminate fibroids but can manage symptoms well enough that some people avoid surgery altogether.
Uterine fibroid embolization (UFE) is a minimally invasive procedure where a specialist blocks the blood vessels feeding the fibroid, causing it to shrink. Recovery typically takes 7 to 10 days, with most people back to normal activities within two weeks. UFE has a lower recurrence rate than surgical removal because it addresses all fibroids at once rather than cutting out individual ones.
Myomectomy is the surgical removal of fibroids while keeping the uterus intact, which makes it the preferred option for those planning future pregnancies. Recovery time varies considerably depending on the approach. A hysteroscopic myomectomy, done through the vagina for fibroids inside the uterine cavity, has the quickest recovery at around three to five days. A laparoscopic approach takes two to four weeks. An open abdominal myomectomy, used for very large or numerous fibroids, requires four to six weeks of recovery. The trade-off with myomectomy is that new fibroids can form afterward, since the procedure removes existing growths but doesn’t prevent new ones.
Hysterectomy, the complete removal of the uterus, is a definitive solution but is generally reserved for people who have completed childbearing and have fibroids that haven’t responded to other treatments.
How They’re Diagnosed
A pelvic ultrasound is the first-line tool for both conditions. It can usually determine whether a growth is solid (suggesting a fibroid) or fluid-filled (suggesting a cyst), where exactly it’s located, and how large it is. In some cases, an MRI provides a more detailed look at fibroids, particularly when surgery is being planned and the surgeon needs a precise map of the growths. For ovarian cysts with unusual features, blood tests may be ordered to help assess the likelihood of malignancy.
If you’ve been told you have a “fibroid cyst,” it’s worth asking your provider to clarify which condition they mean. The distinction matters because the monitoring schedule, treatment options, and long-term outlook are different for each one.