Leiomyosarcoma is a tumor of the smooth muscles

By Jennifer Welsh 

Published on June 16, 2023

 Medically reviewed by Doru Paul, MD

Leiomyosarcoma (LMS) is a very rare, abnormal growth in the smooth muscles of many organs—most often the stomach, intestines, and uterus. Leiomyosarcoma tumors usually spread to other tissues and distant organs. They can be unpredictable—growing and spreading very quickly, making them deadly.¹

Often, leiomyosarcoma doesn't respond well to traditional cancer treatments like radiation and chemotherapy.² While leiomyosarcoma can be deadly, many factors impact a person's prognosis. In the early stages, leiomyosarcoma is even curable.

This article will cover leiomyosarcoma's prognosis, why leiomyosarcoma is life-threatening, and what symptoms to watch for. It will cover treatment options and stages of leiomyosarcoma. 

Luis Alvarez / Getty Images

Leiomyosarcoma Formation: Cancer in Smooth Muscles

Leiomyosarcoma is a cancer that develops in the smooth muscles. These muscles are commonly found in the body's hollow organs, including the intestines, stomach, bladder, and blood vessels.¹ Smooth muscles act without being told to—the brain has no conscious control over them. Their functions include moving blood, helping the gut pass food, and birthing a baby.²

The gastrointestinal (GI) tract (stomach and intestines) and the uterus are the two most common places where leiomyosarcoma develops.² Less commonly, leiomyosarcomas appears in the blood vessels, heart, liver, pancreas, areas of the abdominal cavity, skin, bladder, and urinary tract.

What Is a Sarcoma?

Leiomyosarcoma is a type of soft tissue sarcoma.¹ This type of cancer starts in smooth and skeletal muscles, tendons, fat, lymph and blood vessels, and nerves (the body’s soft tissues and connective tissues).³

At least 15,000 new cases of soft tissue sarcoma are diagnosed in the United States annually, accounting for about 1% of all adult cancers. Leiomyosarcoma accounts for about 10% of them.²¹

Leiomyosarcom a is rare. It affects people of all sexes but is slightly more common in people assigned female at birth. Middle-aged and older adults are more likely to get leiomyosarcoma than children.⁴

Studies have estimated that 3 people out of every 200,000 will develop these tumors per year in Western countries.⁵ About 6 out of every 1 million people get a leiomyosarcoma tumor in the uterus annually in the United States.¹

Leiomyosarcomas that develop in the stomach and intestines are often classified as gastrointestinal stromal tumors (GIST) because of their unique characteristics. They are typically slower growing than other leiomyosarcomas.⁵ Between 5,000 and 6,000 of these tumors are diagnosed annually in the United States.

Getting a Leiomyosarcoma Diagnosis

These smooth muscle cancers are very rare. But they’re aggressive and deadly, especially when not caught early. The only way to detect a leiomyosarcoma, other than through imaging tests, is to watch for signs and symptoms of a tumor.

Symptoms

Depending on the tumor's location, you may feel it as a lump under the skin.¹ There may be some pain or swelling in the area, too.²

Other leiomyosarcoma symptoms depend on the size and location of the cancer and if it has spread to other body parts. As these tumors get bigger, they can interfere with how organs function, causing symptoms related to that. For example:²

• GIST leiomyosarcoma in the digestive tract can cause bleeding and other digestive issues.

• Uterine leiomyosarcoma can cause menstrual changes, for example such as bleeding or discharge.

Benign Leiomyoma vs. Malignant Leiomyosarcoma

When healthcare providers diagnose leiomyosarcoma, they first need to ensure it’s not a similar, benign (non-cancerous) leiomyoma. These are smooth muscle tumors that are not cancerous. Leiomyomas are often called fibroids, especially when they develop in the uterus.⁶ If a fibroid grows after menopause, it should be checked for cancer.⁷

As a leiomyosarcoma gets large and spreads to other organs, it can cause symptoms of metastatic cancer (cancer that has spread to other areas of the body). These include:¹

• Pain

• Losing weight for no reason

• Digestive issues like nausea and vomiting

• Unexplained fatigue²

• Fever

• A general feeling of ill health

Diagnosis

To diagnose leiomyosarcoma, your healthcare provider will ask about your symptoms and medical history and examine your body.

They'll order imaging tests, such as magnetic resonance imaging (MRI), computed tomography (CT), angiography, and positron-emission tomography (PET). The images will give your care team an idea of where and how big the tumor is. They can also help rule out other tumor types and see if it has spread to other organs.¹

They'll also order blood tests to look for signs of cancer. They'll take a small tissue sample called a biopsy to check that a tumor is a leiomyosarcoma.¹

It's also possible they'll go ahead and remove the tumor completely. Surgical resection is the most effective treatment for leiomyosarcoma. After taking the tumor out, the surgeon can remove samples to examine the cancer cells. These can show how aggressive the cancer is and, therefore, if further treatment is necessary.²

Stages of Leiomyosarcoma 

Staging is how healthcare providers compare cancers in different people. It gives them an idea of what treatments may work best and what a person's prognosis may be. Sarcoma staging is based on the size of the tumor, how far it has spread, and how the cancer cells look under the microscope.

Sarcomas are staged from 1 to 4 based on how much they've grown and spread. The higher the stage, the more advanced the cancer. 

The grade of the tumor can be determined by how the cells look under a microscope. When a healthcare provider takes a tumor biopsy, they'll send it to the lab to get graded. Grading describes how abnormal ("wild") the cells look in the microscope and how fast it is likely to grow.⁸

The tumor's grade is determined between 1 and 3; the higher numbers mean the cancer cells look wilder and divide a lot, meaning the tumor is more aggressive. 

The American Joint Committee on Cancer's Version 7 Staging System for Soft Tissue Sarcoma defines sarcoma stages based on tumor size and grade, as outlined below:⁷

• Stage 1A: The tumor is smaller than 5 centimeters (cm), and its grade is 1 or ungradable.

• Stage 1B: The tumor is bigger than 5 cm, and its grade is 1 or ungradable.

• Stage 2A: The tumor is smaller than 5 cm, and its grade is 2 or 3.

• Stage 2B: The tumor is bigger than 5 cm, and its grade is 2.

• Stage 3: The tumor is bigger than 5 cm with a grade of 3, or the cancer has spread to the lymph nodes.

• Stage 4: Any tumor that has spread to distant organs.

The International Federation of Gynecology and Obstetrics (FIGO) also has a staging system specifically for uterine sarcomas. There is less evidence that the tumor's grade is relevant to the prognosis of people with uterine sarcomas, so these stages do not consider the tumor's grade.⁴ These stages are defined as follows:⁷

• Stage 1 tumors are limited to the uterus. In stage 1A, the tumor is smaller than 5 cm; in 1B, it is larger than 5 cm.

• Stage 2 tumors extend beyond the uterus, within the pelvis. Stage 2A tumors have spread to the regions of the ovaries and fallopian tubes. Stage 2B tumors have spread to other pelvic tissues.

• Stage 3 tumors have spread to abdominal tissue. This includes stage 3A, which has spread to one other area in the abdomen; stage 3B, which has spread to more than one area; and stage 3C, which has spread to lymph nodes in the abdomen.

• Stage 4 tumors have spread to other organs. Stage 4A tumors have spread to the bladder or rectum, while 4B tumors have spread to distant organs.

Metastatic Leiomyosarcoma

Generally, stage 4 tumors are called metastatic leiomyosarcomas. These cancers have spread (metastasized) to other areas of the body. The most common sites for leiomyosarcomas to spread are the lungs or liver. New tumors in these locations can cause potentially life-threatening complications.²

A study of uterine leiomyosarcomas found that they spread most frequently to the:⁵

• Lung

• Brain

• Skin or other soft tissues

• Bone

• Other sites (thyroid, salivary gland, heart, liver, pancreas, adrenal gland, bowel, and breast)

Recurrent Leiomyosarcoma

Because it's aggressive and spreads quickly, leiomyosarcoma has a high risk of returning after initial treatment rounds. Even a successfully treated leiomyosarcoma can come back. This is called recurrent leiomyosarcoma.² This cancer can be dormant for years, sometimes returning long after initial treatment.⁵

Uterine leiomyosarcomas recur in up to 70% of cases. Leiomyosarcomas in other parts of the body seem to come back in about 40% of cases.⁷

After Diagnosis: Leiomyosarcoma Treatment Plan 

It is possible to cure leiomyosarcoma if the tumor is caught early, before it spreads. The tumor can often be removed using surgery. Cells left behind during surgery or already spread to other body parts can be destroyed using other systemic treatments, though this is less likely to lead to a cure.¹

Your healthcare provider will immediately begin treatment if you’ve been diagnosed with leiomyosarcoma. Treatment usually starts with surgery to remove the tumor. It’s often followed by radiation or chemotherapy.

The treatments needed depend on your general health, age, and information about your cancer, including where the tumor is located, its size, grade, stage, and if it has spread to other parts of the body.²

Surgery

Surgery is the best treatment for leiomyosarcoma.¹

National Cancer Institute. Leiomyosarcoma.

 Surgery can cure leiomyosarcoma if it’s caught early, hasn’t spread, and can be removed entirely.

Your options for surgery to remove the leiomyosarcoma tumor depend on where it is, how big it is, and if it has spread to other tissues and organs. In some cases of advanced leiomyosarcoma, surgery may not be the best option or an option at all.²

If surgery doesn’t altogether remove the tumor and some cancer cells are left behind—either at the surgery site or that have already spread to other parts of the body—the cancer may come back. Other cases may need additional surgeries to reconstruct the area.

Radiation Therapy

If leiomyosarcoma has spread to other tissues, lymph nodes, or organs, you’ll need additional treatments to help prevent it from coming back. One of these is radiation therapy. It’s often used during or right after surgical removal of the tumor. Radiation therapy uses high-energy beams to break apart the genetic material of the cancer cells, killing them.¹

If your tumor is not a candidate for surgery, you may get radiation therapy alone.

Chemotherapy

Chemotherapy drugs kill dividing cells. Cancer cells, especially aggressive ones, grow and divide often. In leiomyosarcoma, it’s used when the primary tumor is large or if the cancer has spread and grown in other parts of the body. It’s used in combination with surgery.¹

Cancers that have spread to nearby tissues, lymph nodes, and other organs or those that have returned after initial surgery and treatment are likely to need chemotherapy.²

Chemotherapy drugs kill fast-growing cells, which can damage some of the healthy cells in the body, causing side effects such as fatigue and nausea. These side effects may be too much for people who are very old or have other health issues. 

Experimental Treatments and Clinical Trials

Due to the lack of treatment options, new drugs are being developed or tested to treat leiomyosarcoma. These include drugs to prevent the formation of new blood vessels to the tumor and those that prime the immune system to fight cancer.²

You can find out more about clinical trials for leiomyosarcoma at clinicaltrials.gov. 

Leiomyosarcoma Survival and Determining Factors 

Oncologists (cancer specialists) consider leiomyosarcoma aggressive cancer. It grows quickly and spreads easily. Leiomyosarcoma prognosis depends on factors such as:¹

• Location of the tumor 

• Spread of the tumor

• How surgery went

If found early, leiomyosarcoma can be cured. A person’s prognosis is good and full recovery is likely if surgery removes the tumor entirely.

The prognosis is poor when the tumor has grown large or spread to other body parts. This makes treatment more difficult, especially since chemotherapy and radiation are not very effective at stopping these tumors.¹

According to the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program database, the survival rate of leiomyosarcoma is not well known, as this is a rare cancer. However, leiomyosarcomas are more aggressive than other sarcomas, so they generally have a worse prognosis. 

Soft tissue cancers, in general, have five-year relative survival rates of:⁹

• 82.4% for sarcomas discovered while still in the tissue they came from

• 59.8% for sarcomas spread to nearby tissues or lymph nodes

• 16.7% for sarcomas spread to other organs, like the lungs or liver

GIST leiomyosarcoma tumors in the gastrointestinal tract are typically less aggressive. According to the National Cancer Institute, the five-year relative survival rates for GIST from 2012 to 2018 were:¹⁰

• 95% for GIST discovered while still in the GI tract

• 84% for GIST that has spread to nearby tissues or lymph nodes

• 52% for GIST that has spread to other organs

According to the the American Cancer Society, uterine leiomyosarcomas have five-year survival estimates of:¹¹

• 60% for localized disease

• 37% for regional disease

• 12% for metastatic disease

Leiomyosarcoma Patient Support

If you're dealing with a leiomyosarcoma diagnosis and treatment, you'll need support. These rare and aggressive cancers will challenge you emotionally and physically during your treatment journey.¹²

Lean on your loved ones, friends, and care team for support. Look for in-person or online support groups to connect with others dealing with cancer. 

While getting treatment, talk to your care team about any side effects you're dealing with. You may be coping with pain, fatigue, or changes in appetite or body image. 

When possible, try to get some physical activity. Eat well. Talk to a registered dietitian to make sure you're eating the right foods.

Try relaxation techniques such as meditation, deep breathing exercises, or yoga. These can help reduce stress and improve your well-being.

Additional support and resources are available to you. These include counseling services, financial assistance programs, and online communities. Ask your care team about local resources. Work with a counselor or therapist to develop healthy coping mechanisms. They can help you deal with the fears and worries that may develop during treatment.

If you're diagnosed with a terminal form of leiomyosarcoma, talk to your care team about palliative care options. These can help ease your symptoms without the major side effects that traditional treatment might cause.

Summary

Leiomyosarcoma is a rare and aggressive form of cancer. It develops in the body's smooth muscles, most often in the stomach, intestines, and uterus. It grows quickly and spreads to other tissues and distant organs, making it deadly. Traditional cancer treatments like radiation and chemotherapy are less effective against leiomyosarcoma.

Leiomyosarcoma primarily affects adults. Detecting leiomyosarcoma can be challenging. Getting an early diagnosis is crucial for a good outcome.

Symptoms vary depending on the location and size of the tumor. They may include pain, swelling, menstrual changes, weight loss, digestive issues, fatigue, and feeling sick. Healthcare workers use imaging, biopsies, and blood tests to diagnose leiomyosarcoma.

Healthcare providers stage leiomyosarcoma using the tumor's size, spread, and grade. Stages range from 1 to 4, with higher stages indicating more advanced cancer.

Many people with leiomyosarcoma have their cancer come back. Uterine leiomyosarcomas come back in up to 70% of cases. Leiomyosarcomas in other body parts come back about 40% of the time. Metastasis, particularly in the lungs or liver, is a frequent complication.

Treatment for leiomyosarcoma involves surgery to remove as much cancer as possible. Additional treatment with radiation and chemotherapy can cancer cells or is an option when surgery is not. These treatments are not very effective against leiomyosarcoma but may extend lifespan.

Leiomyosarcoma can be challenging to treat, particularly when it has spread to other organs. The prognosis for leiomyosarcoma depends on factors such as tumor location, spread, and the success of surgery. Early detection, proper staging, and comprehensive treatment are crucial for improving outcomes.