Soft tissue sarcoma

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Muscle tissue tumours

Soft tissue sarcomas of the muscle most often develop in smooth muscle. Smooth muscles are involuntary muscles, which means you can’t consciously control them. They include the muscles in the walls of hollow organs such as the bladder.

Soft tissue sarcomas may also develop in skeletal muscle. These are the muscles you can control to move your body.


Leiomyosarcoma is tumour that develops in smooth muscle. It is one of the more common types of soft tissue sarcoma. Leiomyosarcoma usually develops in middle-aged or older adults. These tumours can grow quite large before they cause symptoms and are diagnosed.

Leiomyosarcomas can develop almost anywhere in the body, but they commonly start in the following areas:

  • retroperitoneum (the back of the abdominal cavity)
  • digestive organs (especially the stomach)
  • genitourinary tract organs (such as the uterus, bladder, kidney or prostate)
  • larger blood vessels (such as the pulmonary artery and inferior vena cava)

Leiomyosarcomas often develop in areas where it is difficult to completely remove them with surgery. This means that there is a chance they will come back, or recur, in the same area where they started. This is called local recurrence.

If leiomyosarcomas spread, or metastasize, they tend to spread to the lungs and liver.


Rhabdomyosarcoma is a tumour that develops in skeletal muscle. It is the most common type of soft tissue sarcoma that develops in children. Rhabdomyosarcoma rarely occurs in adults. This tumour is treated in similar ways in adults and children.

Rhabdomyosarcoma usually develops in:

  • a limb
  • the head and neck area
  • the trunk of the body
  • the genitourinary organs, which include the organs of the urinary tract or reproductive organs (such as the vagina or bladder)

The subtypes of rhabdomyosarcoma include:

  • Embryonal tumours occur in the head, neck and eye. They are more common in children than adults. Embryonal botryoid rhabdomyosarcomas develop in organs of the genitourinary system (such as the vagina or bladder). Embryonal spindle cell rhabdomyosarcoma is a rare variation of embryonal rhabdomyosarcoma.
  • Alveolar tumours develop in the muscles of arms and legs. They tend to occur most often in teenagers and young adults.
  • Adult pleomorphic or anaplastic tumours usually develop in the muscles of arms and legs. They tend to occur in middle-aged adults.


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