Sonography & Sonohysterography of the Non-Gravid Uterus

Myometrial Lesions: Fibroids

Fibroids are very common, benign tumors of smooth muscle and connective tissue in the myometrium.

Approximately 20% of women over the age of 35 have fibroids. They're more common in blacks than in whites. They're usually multiple, and they're often estrogen dependent. That means that they enlarge or infarct during pregnancy. Because they are often estrogen dependent, they may decrease in size after menopause.

Ultrasound Appearance of Fibroids

On ultrasound, you will see single or multiple heterogeneous, highly attenuating masses. By highly attenuating means that they partially shadow behind them. In many cases, they may be calcified, and if they're calcified, the calcification may be internal within the fibroid or on the rim of the fibroid. If it's necrotic, there may be some anechoic areas within them.

Examples of Fibroids on Transabdominal and Transvaginal Scans

This is on a transabdominal scan. There's the fundus of the uterus, the woman's bladder. You can see a focal, well-defined mass in the anterior myometrium. This is typical appearance of a fibroid on a transabdominal scan.

Here is a fibroid on a transvaginal scan. Here is the cervix. You can see the endometrium coming up towards the fundus of the uterus, which is up here. The posterior aspect of this uterus, there's a fairly large but well-defined mass, very typical of a uterine fibroid.

Fibroids with Rim Calcification

This is an example of a fibroid with rim calcification. This is the uterus, two different views of the uterus on transvaginal ultrasound. You can see calcification around the rim on the sagittal view and on the coronal or transverse view. Because there's so much calcification in the rim, you really get totally shadowed out. You don't get a look at the fibroid, but you can tell that one must be there because of this calcification. This woman went on to have a CT scan, and here in her uterus, you can see the rim calcification all the way around the fibroid on both of these views.

Submucosal Fibroids

Another kind of fibroid or location of fibroid is a submucosal fibroid. Submucosal fibroid is one that indents into the endometrium. It is actually arising from the myometrium, but because of its location, it projects into the endometrium. Here, you can see this same fibroid, the same submucosal fibroid. Here it is again. This is a coronal reconstruction. There's the fundus of the uterus, endometrium seen here. This structure, which has the same echogenicity as the myometrium, or at least similar to it, is projecting into bulging into the endometrium and the submucosal fibroid.

Subserosal Fibroids

Or they can be subserosal. Here they are projecting out from the peripheral aspect of the uterus or the serosal aspect. Here's a large fundal subserosal fibroid, and here's a much smaller subserosal fibroid in a different patient. It's actually surrounded by a little bit of fluid in the woman's pelvis. There's the fundus and it's in the anterior uterus, in this case, near the fundus.

Pedunculated Fibroids Prolapsing Through the Cervix

Another location for fibroids. Occasionally the fibroids can be on something of a stalk and projecting into the cervix. This is a fibroid prolapsing through the cervix. You can see the stalk here. Or in another view, this is the stalk and the fibroid. When we turn color doppler on, we can see color doppler extending along the stalk and into the fibroid, which is prolapsing through the cervix here.

Uterine Leiomyosarcoma

Another type of myometrial mass is a uterine leiomyosarcoma. This is a malignant tumor. It's a rare tumor, but it can occur. When it does, we wanna make the diagnosis if possible. We'll see in a minute that it's not so easy to diagnose. We don't usually do it. It's thought to sometimes arise from a preexisting fibroid, or it may arise de novo or on its own.

The problem with diagnosing leiomyosarcomas, the reason that we do it is pretty rare to diagnose it before surgery, is because the presentation on ultrasound or the appearance on ultrasound is similar to that of fibroids.

So when would you ever see a myometrial mass and diagnose a leiomyosarcoma or say that you're worried about leiomyosarcoma? The one situation where you would see a myometrial mass and say, I think that may be a leiomyosarcoma instead of just a fibroid, is in the situation where you have a growing myometrial mass in a post-menopausal woman.

If a woman who is postmenopausal has an ultrasound at one point in time and you see a myometrial mass, you're gonna call it a fibroid. That's what it almost certainly is. If she comes back, let's say six months or a year later, two years later, and it's grown, that's rare for fibroids. As I mentioned earlier, fibroids tend to be estrogen dependent. Postmenopausally, estrogen levels are extremely low. So fibroids rarely grow. After menopause, if you see one that grows on sequential scans, that's the situation. You have to be worried that it may be a leiomyosarcoma.

Example of Suspected Leiomyosarcoma

Here's an example. This is a woman who had an ultrasound. She was postmenopausal. We see this focal mass posteriorly on the sagittal view and on the transverse view. You can see that it's measuring about 11 and a half by nine by nine centimeters. We diagnosed a fibroid. She then came back five months later, but now it's much bigger. It's measuring 13 by nine and a half by 11. Quite a bit bigger than this, and it has some fluid or necrotic areas within it. But most importantly, there's been quite marked growth five months later. That growth is not what you would expect to see in a fibroid. You have to be worried that the reason for the growth is that this is not a fibroid, but instead a malignant version or a leiomyosarcoma. She had surgery and this did prove to be a leiomyosarcoma.