ByNicole Angemi
Leiomyomas, otherwise known as fibroids, are tumors of the smooth muscle that can occur in any smooth muscle throughout the body but most frequently occur in the uterus. Fibroids can range in size from an eraser head to the size of a full term infant and larger! These tumors can cause mild to severe problems for woman depending on their size and location within the uterus. They are the most common tumor of the uterus accounting for 30% of hysterectomies in the US. Many women have them and do not even know it. I see them on a daily basis in uterus specimens taken out for other reasons or incidentally during autopsy.
There are 3 types of muscle located throughout the body. Cardiac muscle, skeletal muscle and smooth muscle. Cardiac muscle is specialized muscle tissue that is seen only in the heart. This muscle moves involuntarily- meaning you can not control its movement. A person can not make their heart beat or stop beating. Skeletal muscle is abundant throughout the skeletal system and diaphragm. This type of muscle is called voluntary- meaning you can control it. If you want to extend your leg you can, and usually this muscle doesn’t move involuntarily. Smooth muscle is found in multiple organs throughout the body and is also involuntary. Fibroids can arise in any smooth muscle throughout the body like the ureters of the kidneys, the esophagus, stomach or bowel wall and the uterus for example. Some muscle tissue can be voluntary and involuntary, for example the diaphragm. A person can make themselves take breaths, but most of the day the muscle is working on its own to assist with breathing.
A leiomyoma or fibroid is a benign tumor arising from the smooth muscle wall of the uterus. These tumors are made up of smooth muscle cells and fibrous connective tissue. These tumors can be found in 3 locations within the uterus; subserosal (beneath the outer surface of the uterus), intramural (within the actual muscle wall of the uterus) or submucosal (beneath the lining of the uterus).
In the pathology lab we see leiomyoma specimens in a variety of ways. Sometimes the surgeon will decide the fibroids are too numerous or large, or they are in locations that are not easily resectable and they will do a complete hysterectomy. Other times they will just remove the fibroids only. This is called a myomectomy and can be done by 4 different surgical procedures; Hysteroscopic– where the fibroids are removed through the cervix without making an incision in the abdomen (done with smaller fibroids), Abdominal– in which the fibroids are removed through an incision in the abdomen, Laparoscopic– in which smaller incisions and a camera are used to remove the tumors; or Robotic assisted in which a “robot” is used as an extension of the surgeons arms for a less invasive procedure.
To the left, this is what a normal uterus looks like from the outside (serosal surface). People are usually shocked to see how small it is (less than 1/2 a pound and about 4″). Especially woman because it causes us so many troubles. Compared to this sharpie marker you can appreciate how small it really is. The photo to the right is an open uterus-split into the anterior and posterior halves (front and back). This is the space where a baby grows (endometrial cavity). Its normal appearance is a triangular cavity as seen below. The lining of this cavity is called the endometrium (mucosa). This is the lining that builds up all month and causes a menstrual period. The period tissue then exits the narrow portion of the uterus (cervix)and then into the vagina. The wall surrounding the cavity is the smooth muscle (myometrium).
In comparison, here is the outer surface of a uterus with fibroids. If you look closely, you can actually see these large tumors have their own blood supply. This particular hysterectomy is about 7 pounds and over 8 inches! The size of a newborn baby!
After opening a uterus of this size, all of the fibroid tumors can be seen.
Upon closer inspection of this uterus, the endometrial cavity can be seen. It is the shiny red strip of tissue towards the bottom left of the photo. Compare this uterus cavity to the one of the “normal” uterus above. The normal shape of the endometrial cavity should be triangular. This uterus has so many fibroid tumors that it is actually distorting the shape of the cavity. This distortion causes a ton of problems in woman including moderate to severe pelvic pain, dysfunctional uterine bleeding, problems getting pregnant, problems keeping a pregnancy and painful intercourse. These tumors can also grow so large that they cause abdominal distention giving a pregnant appearance and can compress on adjacent organs. This particular uterus had multiple subserosal and intramural leiomyomas. This is the “normal” appearance of fibroids. They are fibrous, white-pink and have whorled cut surfaces with no hemorrhage or necrosis. These features are consistent with benign leimoyomas.
This next uterus shows leimoyomas in all 3 locations. The endometrial cavity has submucosal fibroids. Because of their location in the endometrium, these myomas place pressure on the uterine lining that builds with each menstrual cycle. This, in turn, can cause heavy bleeding. Even very small submucosal myomas may cause very heavy bleeding.
This next uterus has a similar appearance upon opening. But the leiomyoma to the left looks a little weird or different. Sometimes these fibroids grow so fast and so big that they begin to outgrow their blood supply. This causes the leiomyomas to have a degenerative, dusky yellow, sometimes pink brown appearance. The fibroids can actually begin to calcify and sort of die or partially die. These changes have a specific appearance and are not to be confused with the appearance of a malignant form of leiomyomas- leiomyosarcoma.
Here is an example of a malignant form of a leiomyoma called a leiomyosarcoma. This appearance is more consistent with malignant features. The tumors have soft pink fleshy cut surfaces with areas of necrosis. If a PA opens a uterus and it looks like this- we automatically know something is up. We would over sample these tumors so the pathologist can have enough slides to determine if it is malignant. The treatment for a leiomyoma vs leiomyosarcoma is VERY different.
Sometimes we receive leiomyoma specimens individually, detached from the uterus if the surgeon decides he can remove the tumors and keep the uterus fairly intact. These procedures are sometimes good for woman of child bearing age who are not ready to lose their entire uterus.
This is a specimen from a classic abdominal myomectomy. This procedure just removes the fibroid tumors and is done through an open incision or laparoscopically depending on the size of the fibroids. The round nodules usually come in a medium to large size specimen container. and can range anywhere from the size of a pea to the size of watermelon.
Another surgical option which is the least invasive option for these tumors is a robotic procedure. This technique leaves the uterus or fibroid tumors “morcellated”. A robot-assisted myomectomy uses a robotic system such as the da Vinci to help surgeons remove fibroids while preserving the patient’s uterus. The surgeon controls the robotic instruments attached to the surgical system from a remotely positioned console. These instruments act as a computerized extension of the surgeon’s hands, allowing the surgeon to separate the fibroids from the uterus and restore the patient’s anatomy. This procedure can be used with small incisions on larger fibroids, rather than having to make a huge surgical incision to take them out. The robot essentially goes in and chops up the tissue into morcellated strips within the cavity, so it can come out through a smaller incision. This is what it looks like when we get it in the lab. In the close up photo to the right you can appreciate these morcellated fibroids have a “normal” appearance compared to the intact fibroids above.
Some patients opt for another procedure as a last resort before surgery. Embolization. Uterine fibroid embolization (also sometimes referred to as uterine artery embolization) is performed by trained interventional radiologists by blocking the arteries feeding blood to the tumors, thus allowing them to shrink and preserving the uterus. The entire procedure takes about an hour and is done under conscious sedation as opposed to general anesthesia.
The fibroid tumors actually have their own blood supply as seen to the left. The interventional radiologist will insert a catheter into an artery located in the groin. Under fluoroscopic (X-ray) guidance, the catheter is advanced into the uterine arteries supplying blood flow to the uterine fibroids. Once the catheter is positioned in the uterine arteries, small particles are injected to block blood flow to the uterine fibroids.
These little particles block off the blood supply causing the fibroid to shrink. This procedure has a high success rate. In those patients that do not have success with embolization, hysterectomy or myomectomy is still necessary. Cutting hysterectomy specimens post a failed embolization attempt are neat. The embolization can be seen grossly. The arteries are dilated with little silicone gel beads. It is super cool looking and can be seen on sections submitted to the pathologist for microscopic exam. Unfortunately I do not have a gross photo, but this illustration shows what the beads look like in the vessels.
Finally, another less invasive procedure is an endometrial ablation. This procedure causes scarring of the endometrium in hopes to control bleeding. This procedure is only to be done after a woman has decided she is done having children. To read more about ablation check out my post “Infrequent Gross Finding: Endometrial Cavity,
In most cases of soft tissue tumors- the general rule for sampling is one section per centimeter- meaning if a fibroid is 15cm we would take 15 different pieces of it to show the pathologist under the microscope. The rules of sampling fibroids vary from lab to lab- mainly because uterine fibroids have such a low malignant potential and some pathologists feel it is not necessary to look at a ton of slides on these specimens. Other pathologists would rather see more slides. The bigger fibroids are usually sampled more because they have a higher chance of being abnormal, but for the most part leiomyosarcoma is very rare- especially compared to the amount of these specimens we see on a daily basis.
