Leiomyosarcoma

January 22, 2026

This page was reviewed under our medical and editorial policy by Lee Cranmer, M.D., Ph.D., professor, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte.

Leiomyosarcoma, sometimes referred to as “LMS,” is a type of soft tissue sarcoma that forms in the smooth muscles inside the body’s organs. Leiomyosarcoma most often develops in the abdominal area. It accounts for about 20% of all new sarcoma diagnoses and is more frequently diagnosed in adults than children.

What Is Leiomyosarcoma?

Sarcomas are a group of cancers that develop in the soft tissues of the body, such as the muscles, fat, tendons or blood vessels. Leiomyosarcoma occurs in the smooth muscles that line the inside of the body’s organs, making it a type of soft tissue sarcoma. Smooth muscles carry out functions in the body that do not require the person to consciously think of. For example, smooth muscles may propel food through the intestine or may contract the uterus at the time of a baby’s birth. Leiomyosarcoma most frequently occurs in the:

• Uterus (in women)
• Space at the back of the abdomen (retroperitoneum)
• Stomach or intestines
• Blood vessels
• Other soft tissues such as the heart, liver or pancreas

Leiomyosarcoma Causes and Risk Factors

Although scientists continue to research leiomyosarcoma, they do not yet know the underlying cause of leiomyosarcoma. However, certain rare genetic disorders, such as Li-Fraumeni syndrome, Gardner syndrome, neurofibromatosis type 1 and nevoid basal cell carcinoma syndrome, may make it more likely that someone develops leiomyosarcoma.

Leiomyosarcoma Symptoms and Signs

Which leiomyosarcoma symptoms someone experiences usually depend on which part of the body is affected. If a tumor is small, it may cause no symptoms at all. However, some of the most common signs of leiomyosarcoma are:

• A lump or swelling that may be felt under the skin
• Pain
• Unexplained weight loss
• Nausea or vomiting

When leiomyosarcoma is more advanced, it may also cause symptoms specific to the area where the tumor is located.

Tests for Diagnosing

Cancer doctors may recommend a variety of tests to diagnose leiomyosarcoma.

A physical exam: During such an exam, a doctor checks for any lumps or signs of a tumor.

Imaging tests: X-ray, computed tomography (CT), positron emission tomography, ultrasound or magnetic resonance imaging (MRI) may provide a more detailed look inside the body in order to detect a tumor or determine its size and exact location.

A biopsy: This procedure removes a small tissue sample from the body, which is then examined under a microscope to look for cancer cells. Doctors may perform a fine needle aspiration biopsy, which uses a thin, hollow needle inserted into a tumor, or a conventional biopsy, which may require surgery.

In many cases, accurately diagnosing leiomyosarcoma may require an exam, imaging and a biopsy.

Leiomyosarcoma Stages

After diagnosing leiomyosarcoma, doctors usually use the TNM staging system to stage cancer, which gives it a value that reflects how advanced or widespread the disease is.

The TNM system measures how big a tumor is (T), the number of lymph nodes (N) it has affected and whether it has metastasized (M), or spread. It also assesses cells taken in a biopsy to see whether they look more like normal cells or more like cancer cells. Those that look more normal are considered low grade (G) and those that show more cancerous activity are high grade.

Leiomyosarcoma is then assigned a stage from 1 through 4, sometimes subdivided by letter (e.g., 1a, 1a) and a grade. Generally speaking, cancers with a higher grade and/or stage number are larger, have spread further or are more aggressive.

Leiomyosarcoma stage 1: The tumor is low grade, smaller than 5 centimeters (cm) and has not spread beyond the primary location.

Leiomyosarcoma stage 2: The tumor may be low or high grade, is smaller than 5 cm and has not spread beyond the primary location.

Leiomyosarcoma stage 3: The tumor is high grade or smaller than 5 cm in size, is deep within the tissue and has not spread beyond the primary location.

Leiomyosarcoma stage 4: The tumor is any grade or size and has spread beyond the primary location.

Leiomyosarcoma Treatment

The treatment options for leiomyosarcoma vary depending on a wide range of factors, including the cancer’s size, location and whether it has spread from where it started to other parts of the body.

Surgery

The most common first-line treatment for leiomyosarcoma is surgery. If a tumor is small, easy to reach or both, it is possible that surgery may cure the condition. However, it is often recommended in combination with other treatment options.

Radiation Therapy

Radiation therapy may be used after surgery to kill any remaining cancer cells at the site of the tumor. This may help prevent the cancer from returning.

Chemotherapy

Some patients also receive chemotherapy drugs, which may be used to try to shrink a tumor before surgery or to target any cancer cells that remain in the body after surgery.

Who Treats Leiomyosarcoma?

Leiomyosarcoma patients receive cancer care from a multidisciplinary team of clinical providers, including expert physicians, oncology nurses and specialists in a wide range of fields, including:

• Medical oncologists, who treat cancers, such as leiomyosarcoma, with chemotherapy and other drugs.
• Surgical oncologists, who diagnose and treat sarcomas with surgery. Surgical oncologists focus on cancers that do not involve the bones.
• Orthopedic oncologists, who specialize in using surgery to treat cancer involving the bones. In particular, reconstructive surgeries to maximize function after treatment is a major focus of their work.
• Radiation oncologists, who use radiation therapy to destroy cancerous tissue.
• Pathologists, who examine tissue samples to make sure the diagnosis is correct and to identify other information that may help determine a treatment plan.
• Radiologists, who use imaging tools, such as X-ray machines, CT scanners, MRI scanners and PET scanners to visualize cancers and determine their extent.
• Interventional radiologists, who use imaging techniques such as X-ray machines, and scanning machines (CT, MRI) in order to undertake procedures that aid the diagnosis and management of cancer. For example, interventional radiologists often undertake biopsies to obtain a specimen of a tumor for diagnosis.
• Supportive care providers, who focus on cancer- and treatment-related side effects and symptom management

Leiomyosarcoma Prognosis

When it is found at an early stage, the five-year survival rate for leiomyosarcoma is around 63%. If the cancer has spread within the same region as the primary tumor, the five-year survival rate is approximately 36%. If leiomyosarcoma spreads to distant body sites, the five-year survival rate is about 14%.

It’s important to talk to the care team to get a personalized prognosis that takes the patient’s leiomyosarcoma stage, grade and other factors into account.