Leiomyosarcoma is a very rare form of cancer, so uncommon that you might never have heard of it before you or a loved one is diagnosed. It’s a type of sarcoma, a group of cancers that grow in tissues that connect, surround, and give strength to your body. These include muscles, cartilage, blood vessels, bones, tendons, and nerves.
Sarcomas make up just 0.7% of all cancers. And out of all sarcomas, leiomyosarcoma accounts for only 5% to 10%.
Causes
Doctors don’t know exactly what causes leiomyosarcoma. Radiation therapy for cancer you had in the past can raise your risk. We don't know if exposure to high doses of dioxin or certain weed killers can lead to it.
This aggressive cancer often starts in the smooth muscle cells lining small blood vessels. But it may also begin in bones or in internal organs like your intestines or uterus.
About half of leiomyosarcomas form in the abdomen, specifically in an area called the retroperitoneum. Women are twice as likely to get these cancers as men are. Most people get them in their 50s or 60s
Symptoms
Many leiomyosarcomas don’t cause symptoms at first. Clues include lumps or swelling as the tumor grows and pain if the tumor squeezes a nerve or muscle. If you have any of these symptoms, especially if the lump is deep in a muscle or comes back after you had a lump removed, see your doctor.
For leiomyosarcomas in the abdomen, early signs can include pain, weight loss, nausea, or throwing up. These tumors can grow to over 4 inches across.
In the uterus, the symptoms are often mistaken for fibroids in imaging tests. A pathologist, which is a scientist trained to identify disease, can examine uterine tissue after a hysterectomy (surgery to remove the uterus) and make the diagnosis.
Types of Leiomyosarcomas
Leiomyosarcomas belongs to one of five types that are based on where they form in your body:
- Retroperitoneal (in the abdomen)
- Cutaneous (in the middle layer of the skin, known as the dermis)
- Vascular (in blood vessels)
- People with compromised immune systems (due to conditions such as HIV or certain medications)
- Bone (extremely rare)
Stages
Another way of looking at sarcomas is by grading and staging. The grade of a cancer is based on how its cells look under a microscope and predicts how fast that cancer may spread.
It can be hard to grade sarcomas, in part because they’re so uncommon. Low-grade cancer cells appear similar to normal cells, tend to grow slowly, and aren’t very likely to spread to other parts of the body. High-grade cancers, on the other hand, have cells that look unusual, grow faster, and are more likely to spread, or "metastasize."
Staging also describes a cancer’s size and location. These details help your doctor know which treatment you need. There are different staging systems for leiomyosarcomas that begin in a woman’s uterus and for those that start elsewhere.
For leiomyosarcoma in the uterus, stages range from I (growing only in the uterus) to stage IVB (has spread to distant places like the lungs, may or may not have spread to nearby lymph nodes or grown into other parts of the pelvis or abdomen).
For leiomyosarcomas that start in other parts of the body, categories range from stage IA (low-grade, small, no signs that the disease has spread) to stage III (high-grade, large, but hasn’t spread to distant parts of the body) and stage IV (tumor has spread to lymph nodes or other body parts).
