What is Leiomyosarcoma of Muscle

A leiomyosarcoma is a smooth muscle tumour.

Muscle is the tissue responsible for body movements and the changes in the shape and size of internal organs. It consists of parallel arrangements of highly specialised cells containing contractile elements – chiefly actin and myosin filaments.

There are 2 main types of muscle (based on their appearance under the light microscope): smooth muscle and striated muscle. Smooth muscle is the muscle that is found in the gastrointestinal, respiratory and genitourinary tracts, the blood vessels, the iris and ciliary body of the eye, the scrotum, and in the hair follicles. Smooth muscle is specialised for a slow and prolonged contraction, and may contract in a wave-like manner (peristalsis) or may remain contracted for an extended period of time without becoming fatigued. Smooth muscle contraction is regulated by the autonomic nervous system.

Statistics on Leiomyosarcoma of Muscle

It is rare, accounting for between 10 and 20% of soft tissue sarcomas. Soft tissue sarcomas are uncomon accounting for 1-2% of all cancers. It occurs with highest incidence in adulthood, with sex incidence being more common in women.

Geographically, the tumour is found worldwide.

Risk Factors for Leiomyosarcoma of Muscle

The aetiology (cause) of leiomyosarcoma is unknown. The risk factors in the development of soft tissue sarcoma include certain familial syndromes such as neurofibromatosis (benign tumours that form on nerve endings or in the skin); Gardner’s syndrome and Li-Fraumeni syndrome; prior radiation; chronic lymphoedema; and exposure to some rare chemical agents.

Progression of Leiomyosarcoma of Muscle

This type of tumour spreads by continuous extension into adjacent structures. Haematogenous dissemination with distant metastases to the lungs and liver can also occur.

How is Leiomyosarcoma of Muscle Diagnosed?

General investigations may show anaemia or a low platelet count if bone marrow is involved or if there has been extensive haemorrhage into the tumour. Abnormal liver function tests suggest liver metastases.

Prognosis of Leiomyosarcoma of Muscle

Prognosis for leiomyosarcoma is dependent upon the histological grading of the tumour and on its size. Superficial tumours discovered early in their course are associated with a good prognosis, and there is a 5 year survival rate of approximately 90%. Larger tumours diagnosed later in their development can cause death through local extension and metastatic deposits. For example, the 5 year survival rates from uterine leiomyosarcoma are only 50% for stage I disease and fall to less than 20% when there are metastases present outside the uterus.

How is Leiomyosarcoma of Muscle Treated?

Treatment of leiomyosarcoma revolves around surgical excision. Radiotherapy may be a useful additive to improve local control or where a cancer is inoperable. In some cases of high-grade leiomyosarcoma, chemotherapy may have a role to reduce the risk of recurrence or to improve operability.

It is important to realise that the treatment of leiomyosarcoma is a complicated process. Associated with the treatment of the disease are the very real long-term sequelae of these treatments in those in whom they establish a cure. The surgical sequelae can be serious and immediately evident following wide excision of primary tumours. Consequences of the very high doses of radiotherapy required to establish control of the disease are less evident initially but develop following a lag period of some ten to fifteen years. These depend on the age of the patient and site of disease, but radiation of large fields, as is often required, can have serious adverse effects on internal organs. In addition, the development of post-radiation tumours such as osteosarcoma is a very real problem. As patients with leiomyosarcoma tend to be older than those with rhabdomyosarcoma these complications of treatment tend to pose less of a problem.

Improvement in symptoms is an important measurement. Specific monitoring may take place through careful clinical follow-up and regular investigations including chest x-ray to exclude pulmonary metastases which could be resected.

The symptoms that may require attention are somatic pain from bone metastases, visceral pain from lung metastases and neurogenic pain if nerve tissue is compressed. Coughing and breathlessness from lung involvement may require specific treatment.

Additional symptoms due to the specific sites involved may require specialist treatment approaches. These can include problems such as lymphoedema where tumours compress the lymphatic drainage of a limb.

(Source: Dr David Dalley, St Vincent’s Hospital).