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GIST Support International - Glossary of Terms
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leiomyomaNon-malignant tumor of smooth muscle cells.
leiomyosarcomaSarcoma of smooth muscle cells. Prior to the discovery in 1998 that KIT expression could distinguish GISTs as a separate type of sarcoma, most GISTs were diagnosed as leiomyosarcoma.
ligandA ligand is a molecule that binds to (links to and forms a complex with) a specific complementary site on another molecule. For example, growth factors are ligands for corresponding growth factor receptors. With respect to GIST, the KIT ligand binds to and activates the KIT receptor in normal cells, but KIT becomes activated without its ligand in GIST.
loss of heterozygosityAllelic heterozygosity is a state in which genetic material from each of the two parents is present in the cell. Loss of heterozygosity (LOH) is caused by a deletion, mutation, or loss of an entire chromosome (or a region of the chromosome) from the cell nucleus. LOH results in a deletion of one of the parent's genetic material to part of the genome. LOH is a common occurrence in cancer. It often indicates the presence of tumor suppressor gene in the lost region. Frequently, the remaining copy of the tumor suppressor gene will be inactivated by a mutation. Loss of heterozygosity can arise by two methods. In the first, a region of a chromosome is deleted, resulting in only one copy remaining. In the second, genetic recombination leaves the cell with two copies of the chromosomal region, but both come from the same parent. For an illustration see this PubMed book link.
lumenThe hollow food passageway of the gastrointestinal tract.

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