Leiomyosarcoma


Leiomyosarcoma, is a malignant smooth muscle tumor. A benign tumor originating from the same tissue is termed leiomyoma. While it has been believed that leiomyosarcomas do not arise from leiomyomas, there are leiomyoma variants for which classification is evolving.
About 1 in 100,000 people get diagnosed with leiomyosarcoma each year. LMS is one of the more common types of soft-tissue sarcoma, representing 10 percent to 20 percent of new cases. Sarcoma is rare, consisting of only 1 percent of cancer cases in adults. Leiomyosarcomas can be very unpredictable. They can remain dormant for long periods of time and recur after years. It is a resistant cancer, meaning generally not very responsive to chemotherapy or radiation. The best outcomes occur when it can be removed surgically with wide margins early, while small and still in situ.

Mechanism

Smooth muscle cells make up the involuntary muscles, which are found in most parts of the body, including the uterus, stomach and intestines, the walls of all blood vessels, and the skin. It is therefore possible for leiomyosarcomas to appear at any site in the body. They are most commonly found in the uterus, stomach, small intestine and retroperitoneum.
Uterine leiomyosarcomas come from the smooth muscle in the muscle layer of the uterus. Cutaneous leiomyosarcomas derive from the pilo-erector muscles in the skin. Gastrointestinal leiomyosarcomas might come from smooth muscle in the GI tract or, alternatively, also from a blood vessel. At most other primary sites—retroperitoneal extremity, truncal, abdominal organs, etc.—leiomyosarcomas appear to grow from the muscle layer of a blood vessel. Thus, a leiomyosarcoma can have a primary site of origin anywhere in the body where there is a blood vessel.
The tumors are usually hemorrhagic and soft and microscopically marked by pleomorphism, abundant abnormal mitotic figures, and coagulative tumor cell necrosis. There is a wide differential diagnosis, which includes spindle cell carcinoma, spindle cell melanoma, fibrosarcoma, malignant peripheral nerve sheath tumor and even biphenotypic sinonasal sarcoma.

Diagnosis

Diagnosis of LMS is made by performing a soft tissue biopsy and examining its histopathology.

Treatment

Surgery, with as wide a margin of removal as possible, has generally been the most effective and preferred way to attack LMS. If surgical margins are narrow or not clear of tumor, however, or in some situations where tumor cells were left behind, chemotherapy or radiation has been shown to give a clear survival benefit. While LMS tends to be resistant to radiation and chemotherapy, each case is different and results can vary widely.
For metastatic disease, chemotherapy and targeted therapies are the first choices.
Chemotherapy regimens are: doxorubicin/ ifosfamide and doxorubicin combination/gemcitabine and docetaxel/ trabectedin
pazopanib is the targeted therapy used in metastatic leiomyosarcoma as second line and is well tolerated.
LMS of uterine origin often respond to hormonal treatments. As of 2020, there are several active clinical trials for uterine LMS.

Notable cases

People who have had leiomyosarcoma include: