GIST Support WikiQUESTION: Can anyone tell me the difference between leiomyosarcoma and GIST and what year it was discovered that there was a difference.
MARINA'S ANSWER: Leiomyosarcoma and GIST are two different diseases. Both are forms of soft tissue sarcoma. Leiomyosarcoma is a cancer of involuntary (smooth muscle). ILMS can arise virtually anywhere in the body, because smooth muscle is everywhere...all our organs, limbs, even skin. Uterine Leiomyosarcoma seems to be the most common form (common uterine fibroids are a benign version, where as LMS is the malignant version). LMS is in the legs is next.
There is true LMS from the GI tract, which would mean it arose from the smooth muscle cells that line the wall of the GI tract. True LMS is not as common as GIST however.
GIST arises from the specialized cells that relay the nerve impulse to the smooth muscle--to make the contracting wave motion of digestion. The normal counterpart of GIST is the "interstital cells of Cajal"--which are a bit nerve like, and a bit muscle like. GIST arises either from ICCs or more likely, their more primitive precursors--stem cells.
GIST and LMS share common appearances under the microscope and until year 2000, pathologists lacked tools to distinguish between them. Manyof us diagnosed before 2000 were told we had leiomyosarcoma (even though it was a GIST). We can't really say that they were misdiagnosed, since GIST was so poorly understood. LMS does not express the KIT protien...Many GISTs including my own don't express any smooth muscle markers.
I will say that my own GIST was diagnosed as GIST even back in 1997 by a place in Seattle though it was also called Leiomyosarcoma by places like MD Anderson and UCLA. I was confused about which disease that I really had until the summer of 1999, when I went to Dana Farber for the first time, and Christopher Fletcher had definitively diagnosed it as GIST even without the benefit of the KIT staining that is the hallmark feature for diagnosis.
Much of the older scientific literature has LMS and GIST confused--and not separated, and so the literature is unreliable. Many GIST pts who were on the internet before year 2000 were affiliated with a Leiomyosarcoma support group...we thought that we had "GI LMS"
LMS is treated differently than GIST. It does not respond to Gleevec. IT is treated with the standard forms of cytotoxic chemotherapy like MAID and AIM. These days a typical GIST is more treatable than LMS.
JULIE ADDS: Adding to what Marina has said: In those rare cases when the pathologist has a hard time differentiating these 2 sarcomas, there is a new test at MD Anderson based on gene expression.
Here is a link to a free paper about it: http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=DetailsSearch&Term=17360660%5Buid%5D