This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was updated on April 21, 2023.

Leiomyosarcoma is a rare and aggressive type of soft tissue sarcoma, which is a cancer of the nerves, muscles, fat and other soft tissues that surround, support and connect the structures of the body.

Leiomyosarcoma grows in the smooth muscles that involuntarily move blood, nutrition and other material throughout the body. These muscles are located in the body’s hollow organs, including the blood vessels, intestines, stomach, bladder and uterus. Leiomyosarcoma usually occurs in the abdomen and uterus, and it may travel through the bloodstream to spread to other parts of the body.

According to the National Cancer Institute (NCI), leiomyosarcoma accounts for approximately 10 to 20 percent of soft tissue sarcoma cases. Soft tissue sarcomas account for 1 percent of cancers diagnosed in adult patients, and leiomyosarcomas account for 7 to 11 percent of those cases, according to the National Organization for Rare Disorders.

This overview will cover the basic facts about leiomyosarcoma, including:

What is a leiomyoma vs. leiomyosarcoma?

Leiomyosarcoma and leiomyoma occur in the smooth muscles of the body. But one key distinction differentiates the two conditions: Leiomyomas are benign (non-cancerous) fibroid growths that don’t spread to other parts of the body, although they may cause pain and other symptoms that require treatment, while leiomyosarcomas are a form of cancer that may spread to other areas of the body.

Types of leiomyosarcoma

The different types of leiomyosarcoma are classified based on the location of the cancer in the body.

Somatic soft tissue leiomyosarcoma

Somatic soft tissue leiomyosarcoma is the most common type of leiomyosarcoma. It affects the connective tissues of the body that support and protect other tissues and organs. Somatic soft tissue leiomyosarcoma has a high potential for metastasis.

Cutaneous or subcutaneous leiomyosarcoma

Cutaneous refers to the conditions of the skin, and subcutaneous describes those beneath the skin. Cutaneous or subcutaneous leiomyosarcoma are rare, slow-growing forms of soft tissue sarcomas that affect the piloerector muscles of the eyes and skin. The piloerector muscles dilate the pupils and cause the hair on the skin to stand up—the sensation of feeling “goosebumps.” Subcutaneous leiomyosarcoma may be more complex to treat and has a higher chance of metastasis than the cutaneous form.

Leiomyosarcoma of a vascular origin

Leiomyosarcoma of a vascular origin is the rarest form of leiomyosarcoma. It may develop in any of the major blood vessels of the body, including the pulmonary artery or peripheral arteries that transport blood to the abdomen and extremities. More than half of vascular leiomyosarcoma cases involve the inferior vena cava, which is the largest vein in the body and carries oxygen-depleted blood from the lower part of the body back to the heart.

Leiomyosarcoma symptoms

Symptoms of leiomyosarcoma vary depending on where the cancer forms in the body and how far it’s progressed. Cancer patients may experience systemic changes that affect their overall health and/or cause symptoms specific to the structures directly affected by tumor growth.

Symptoms of leiomyosarcoma may include:

  • Pain
  • Fever
  • Fatigue
  • Nausea and vomiting
  • Unintentional weight loss
  • A lump under the skin
  • Swelling near the tumor

Possible symptoms of leiomyosarcoma of the digestive system:

  • Abdominal bloating/pain
  • Loss of appetite
  • Dark stools (due to the presence of blood)
  • Vomiting of blood

Possible symptoms of uterine leiomyosarcoma:

  • Changes in bladder and bowel habits
  • Unusual vaginal discharge
  • Unusual vaginal bleeding (unrelated to a period)

It’s not uncommon for patients to have no symptoms in the early stages and only become symptomatic as the tumor begins to grow.

Who is at risk?

Medical experts haven’t determined leiomyosarcoma causes. At this time, it doesn’t appear to be a hereditary condition, but some genetic conditions have been shown to be associated with leiomyosarcoma, including:

Leiomyosarcoma affects both men and women, and this type of cancer is more common in adults than children. Only an estimated 20 to 30 children are diagnosed with leiomyosarcoma annually in the United States, according to the NCI.

How is leiomyosarcoma diagnosed?

The following tests are used to diagnose leiomyosarcoma and determine tumor presence, size and location:

If a mass is detected, the doctor performs a biopsy to confirm the type of tumor. This procedure involves using a small needle to retrieve a sample of the affected tissue. The tissue is then examined under a microscope to diagnose the condition and determine the course of treatment.

Leiomyosarcoma treatment

Leiomyosarcoma treatment varies depending on the location and size of the tumor. Treatment may consist of:

Surgery: Surgical excision and removal of the tumor and surrounding tissue is considered the first-line form of treatment for leiomyosarcoma, when possible and appropriate.

Radiation therapy: Radiation therapy uses high doses of radiation to destroy cancer cells and shrink tumors. It may be used before, during or after surgery.

Chemotherapy: Chemotherapy involves the use of certain drugs to kill cancer cells or to stop them from growing and dividing. This treatment is often prescribed in cases where the tumor is large or when cancer has spread to other areas of the body.

Leiomyosarcoma prognosis

The long-term prognosis for patients with leiomyosarcoma depends on a range of factors, including:

  • Where the cancer is located
  • How far it’s progressed
  • How it responds to treatment
  • The patient’s age and health at the time of diagnosis

When localized leiomyosarcoma is detected and treated before it has the chance to spread to other parts of the body, treatment typically increases the patient’s longevity.

If the tumor is large or cancer has already spread to other parts of the body, treatment may be more challenging. Leiomyosarcoma is considered an aggressive, rapidly-growing cancer. It’s important that patients discuss symptoms and concerns with their cancer care team as soon as possible and avoid delays in seeking care

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