GIST Glossary 
A
Adjuvant therapyRefers to additional treatment given after a main mode of therapy (the main treatment is usually surgery). For example, Gleevec given after surgery in hopes of preventing or delaying a recurrence is adjuvant therapy.
AlleleOne of the variant forms of a gene at a particular location on a chromosome. Different alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one).
Amino acidsChemical building blocks from which proteins are assembled; there are twenty types of amino acids in proteins.
AnemiaAnemia is a lower than normal number of red blood cells (erythrocytes) in the blood, usually measured by a decrease in the amount of hemoglobin. Hemoglobin is the red pigment in red blood cells that transports oxygen.
AngiogenesisThe growth of new blood vessels.
AntibodyA type of protein, produced by cells of the immune system, which recognizes and binds to specific molecules, such as other proteins; synonym: immunoglobulin.
ApoptosisControlled cell death, a type of cellular suicide where the cell issues its own death warrant
Autosomal dominant geneA dominant gene that occurs on a non-sex chromosome (excludes the x and y chromosomes).
B
BenignNot malignant or cancerous.
C
CarcinomaCancer that occurs in epithelial tissues, such as the cells that form the surfaces of skin, lung, bladder, colon, etc. (See also: sarcoma, leukemia).
C-kitThe name of the gene that contains the instructions for manufacturing the “KIT” protein. When referring to the gene, “c-kit” is correct; when referring to the protein, the correct terminology is “KIT”. When a pathologist tests (using stains) for the KIT protein on tumor cells, the test is often called c-kit or CD117.
CT scan (CAT scan)Computerized (Axial) Tomography: reconstruction of a three-dimensional view of the inside of the body, by analyzing a series of two-dimensional X-ray images taken from many different angles.
ChemoembolizationA technique for attacking liver metastases by injecting chemotherapy directly into the blood vessels that feed the liver tumor; a drug, mixed with particles that embolize or block the flow of blood, is injected through a catheter (inserted into an artery in the groin) into the artery in the liver that supplies blood flow to the tumor.
ChemotherapyDrug therapy, especially for cancer.
ChromosomeOne of the threadlike “packages” of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.
CryosurgeryDestruction of tumor tissue using sub-zero temperatures; a stainless-steel probe is positioned in the center of the tumor; liquid nitrogen (which is extremely cold) is circulated through the end of the probe.
Cytochrome P450See P450.
D
DesquamativeRelating to desquamation; The shedding of the outer layers of the skin. The word comes from the Latin “desquamare” meaning “to scrape the scales off a fish.”
DiureticA drug (e.g., hydrochlorothiazide, furosemide, or zaroxolyn) that promotes urination; prescribed to treat edema or high blood pressure.
DNAThe biological macromolecule that encodes genetic information; contained in the chromosome. Chemically, DNA is a polynucleotide, a polymer made up of very many subunits (deoxyribonucleotides) linked in a linear sequence. The four sub-units are A, C, G, and T.
DNA hypermethylationDNA methylation is a process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter, DNA methylation typically acts to repress gene transcription.
Alterations of DNA methylation have been recognized as an important component of cancer development. Hypermethylation is associated with gene promoters and can arise secondary to gene (oncogene suppressor) silencing but might be a target for epigenetic therapy.
DomainA structural/ functional region of a protein.
E

Edema

Fluid retention in the body.
EnzymeA protein which catalyzes (accelerates the rate of) a chemical reaction.
Epimutant SDH-deficient GISTTumor tissue is SDHB IHC negative and mutation test shows no SDH A, B, C or D mutations. Confirmable by separate testing for SDHC hypermethylation. This is important to distinguish from other forms of SDH-deficient GIST as due to its hypermethylated nature it may respond to different treatments.
ExonPortion of a gene which contains sequence information encoding the amino acid sequence of a protein; specific exons usually correspond to specific domains of a protein.
F
FumarateA salt or ester of fumaric acid. (Fumaric acid is produced in eukaryotic organisms from succinate in complex 2 of the electron transport chain via the enzyme succinate dehydrogenase. The salts and esters are known as fumarates. - Wikipedia.)
G
GastricPertaining to the stomach
GastrectomyThe surgical removal of all or part of the stomach.
Gastrointestinal Stromal Tumors (GIST)A specific type of sarcoma, arising along the gastrointestinal tract, characterized by expression of c-kit protein.
GleevecAn oral molecularly-targeted chemotherapy. It is first-line treatment for GIST and Chronic Myeloid Leukemia (CML). Gleevec inhibits several enzymes that drive certain cancers. This includes the bcr/abl enzyme in CML, and KIT and PDGFRα in GIST.
H
HepaticPertaining to the liver.
HistologyThe branch of the science of anatomy which deals with the microscopic structure of tissues.
HyperplasiaA general term referring to the proliferation of cells within an organ or tissue beyond that which is ordinarily seen.
Hypoxia-inducible factor (HIF) Hypoxia-inducible factors (HIFs) are transcription factors that respond to decreases in available oxygen in the cellular environment, or hypoxia. There is a critical role for HIF-1 in the regulation of genes involved in a variety of important biological processes that include glucose transport and metabolism, vascular growth, vasomotor regulation, erythropoiesis, iron metabolism, and catecholamine synthesis.
I
ImatinibThe “generic” name for the drug Gleevec.
ImmunoglobinSee antibody
Immunohistochemistry (IH, IHC, or IHC Stain)A lab test that uses antibodies to test for certain antigens (markers) in a sample of tissue. The antibodies are usually linked to an enzyme or a fluorescent dye. When the antibodies bind to the antigen in the tissue sample, the enzyme or dye is activated, and the antigen can then be seen under a microscope. Immunohistochemistry is used to help diagnose diseases, such as cancer. It may also be used to help tell the difference between different types of cancer. In GIST, an IHC stain is used to confirm an initial GIST diagnosis, and a separate IHC stain to test whether a patient has the SDH-deficient version of the disease.
Inducer (for example, of cytochrome P450)A drug (or other chemical) which causes an increase in the expression of an enzyme (P450) which metabolizes another drug.
InhibitorA compound (e.g. drug) which blocks the activity of an enzyme; Gleevec works by inhibiting c-kit.
Interstitial Cells of CajalSpecialized cells, found throughout the gastrointestinal tract that are essential for normal gastrointestinal motility; these are the cells from which GISTs arise.
IntraperitonealAdministered through the peritoneum (See peritoneum).
J
K
KinaseAn enzyme which catalyzes a phosphorylation reaction (addition of a phosphate group to a molecule) (Pronunciation: rhyme a with “fine days”)
KindredA group of related persons.
KITA protein, expressed on Interstitial cells of Cajal, which regulates their replication; GIST cells usually express a mutated form of KIT.
Krebs CycleThe sequence of reactions by which most living cells generate energy during the process of aerobic or oxygen-based respiration. SDH is a key component of this cycle, and when it is deficient the cycle is affected.
L
LeukemiaCancer arising in cells of the blood (See also: carcinoma, sarcoma).
Local recurrenceA tumor grew back in the same spot where it was surgically removed.
M
MalignantCancerous; tending to grow and metastasize (opposite of “benign”).
Mesenchymal cellsA general class of “connective” cells that includes fibroblasts, muscle cells, and blood vessel lining cells; sarcomas arise from these cells.
MetastasisThe spread of a tumor, through the circulation, to a site distant from the original tumor; e.g., metastasis of GIST to the liver. Metastatic cancers are usually more difficult to treat than are localized tumors. (Pronunciation: mu-TA-stu-sis).
MitosisCell division (pronounced my-TOE-sis).
Mitotic countThe number of cells (as seen under the microscope) undergoing cell division; generally, a higher mitotic count indicates a more active (malignant) tumor.
MRI (Magnetic Resonance Imaging)A radiological technique in which the patient is placed in a powerful magnet, and the magnetic properties of the nuclei of water (or other molecules) are used to construct anatomical images. MRI images somewhat resemble those produced by CT scans, but MRI is more sensitive to soft tissue structures. Unlike CT or PET scans, no ionizing (high-energy) radiation is used in MRI.
MutationA change in the sequence of nucleotides in a gene, often resulting in a change of the sequence of amino acids in a protein.
Mutant SDH-deficient GISTTumor tissue that is SDHB IHC negative and SDH gene mutation tests positive for SDH A, B, C or D mutation.
Somatic Mutant SDH-deficient GIST - Tumor tissue that is SDHB IHC negative. SDH gene mutation test is positive for SDH A, B, C or D mutation. Normal tissue (cheek swab) SDH mutation test shows no mutations in SDH A, B, or C.
Germline Mutant SDH-deficient GIST - Tumor and normal tissue (cheek swab) test positive for the same SDH A, B, C or D mutation.
N
NeoadjuvantNeoadjuvant therapy is treatment given before the main treatment; For example, Gleevec given before surgery to try to shrink a tumor(s) is neoadjuvant therapy.
NephrotoxicDamaging to the kidneys.
NucleotideChemical subunit of RNA or DNA (strictly speaking, the DNA subunit is a deoxynucleotide, but the term is often used more loosely).
NeutropeniaA blood disorder characterized by a low number of neutrophils. Neutrophils are a type of white blood cells that fight infection. See Wikipedia article

There are four general guidelines (used to classify the severity of neutropenia based on the absolute neutrophil count (ANC) measured in cells per microliter of blood:

Neutropenia (1500 < ANC < 2000) — slight risk of infection

Mild Neutropenia (1000 < ANC < 1500) — minimal risk of infection

Moderate Neutropenia (500 < ANC < 1000) — moderate risk of infection

Severe Neutropenia (ANC < 500) — severe risk of infection

O
ObligateAn adjective meaning “by necessity” (antonym facultative) and used mostly in biology.
OmentumA fold of the peritoneum (See peritoneum below) extending from the stomach to adjacent organs in the abdominal cavity.
OncogeneA gene involved in promoting or regulating cell growth. When activated by specific mutations, these genes contribute to or cause cancer development. (See also: tumor suppressor gene).
P
P450A class of enzymes which catalyze the metabolism of drugs; there are about a dozen different P450 enzymes in human liver; P450 3A4 is the most abundant.
PDGFRαPlatelet-derived growth factor receptor alpha: a protein closely related to KIT, which was recently (2003) found to be activated in some cases of GIST.
PDGFRbPlatelet-derived growth factor receptor beta: a protein that is involved in the formation of new blood vessels (See angiogenesis).
PenetranceA term used in genetics that describes the extent to which the properties controlled by a gene, its phenotype, will be expressed. A highly penetrant gene will express itself almost regardless of the effects of environment, whereas a gene with low penetrance will only sometimes produce the symptom or trait with which it has been associated.
PeritoneumThe transparent membrane lining the walls of the abdominal cavity, enclosing the stomach and intestines.
PET (Positron Emission Tomography)Reconstruction of a three-dimensional view of the inside of the body by the radiation emitted from a radioactive tracer administered to a patient.
PhosphorylationAddition of a phosphate group; this is a common chemical modification of proteins and often alters the activity of an enzyme.
ProbandThe first affected person that seeks medical attention for a genetic disorder.
Promoter HypermethylationPromoter hypermethylation is an important pathway for the repression of gene transcription in cancer.
ProteinA biological macromolecule comprised of many (more than 100) amino acids linked together (by peptide bonds) in a specific sequence. Almost all enzymes (biological catalysts) are proteins. KIT and PDGFRα are proteins.
Q
QuartileA quartile is any of the three values which divide the sorted data set into four equal parts, so that each part represents 1/4th of the sampled population.
R
RadiologyThe medical study of anatomical images produced by (originally) X-rays and (now, more generally) any imaging technique, including MRI, ultrasound, CT and PET scanning.
ResectionSurgical removal of a tumor (or other material).
RFA (radio-frequency ablation)A technique that destroys liver tumors by heating them to high temperatures. A thin needle is inserted into the tumor and electrical current is passed through the tip.
RNAThe biological macromolecule that converts genetic information contained in DNA into a form that the cell can use to make proteins. is a polynucleotide, a polymer made up of very many subunits (deoxyribonucleotides) linked in a linear sequence. The four sub-units are A, C, G, and T.
RT-PCRReverse transcriptase polymerase chain reaction: a sensitive indirect method for measuring the expression of a protein in a cell or tissue, by analyzing the level of the messenger RNA encoding the protein.
S
SarcomaCancer that occurs in connective tissues, bones, and muscle. (See also: carcinoma, leukemia).
SDH-deficient GISTGIST tumor tissue that stains negative for SDHB IHC.
SGOT (serum glutamate-oxaloacetate transaminase)An enzyme, abundant in liver, which is released from cells following damage to the organ. Assay of this enzyme activity in blood serum is used to detect possible hepatotoxicity. SGPT (serum glutamate-pyruvate transaminase) is also used similarly.
SuccinateA salt or ester of succinic acid.
Succinate dehydrogenase (SDH) SDH is an enzyme. Enzymes typically act as catalyzers or substances that initiate or increase the rate of a chemical reaction, often dramatically. SDH speeds up the conversion of succinate to fumarate. This conversion is a key part of cell metabolism. SDH has four components (A, B, C & D). All four combine to form the SDH complex. If one component is faulty the complex cannot work. SDH is a key component of the cell energy cycle called the Krebs cycle that drives every cell.
Sutent (SU11248, Sugen, Sunitinib)An oral molecularly-targeted chemotherapy. Sutent was approved on January 26, 2006 in the United States for patients whose disease has progressed on Gleevec or who are unable to tolerate treatment with Gleevec. Sutent inhibits several enzymes that drive certain cancers. These include; platelet-derived growth factor receptors (PDGFRα and PDGFRβ), vascular endothelial growth factor receptors (VEGFR1, VEGFR2 and VEGFR3), stem cell factor receptor (KIT), Fms-like tyrosine kinase-3 (FLT3), colony stimulating factor receptor Type 1 (CSF-1R), and the glial cell-line derived neurotrophic factor receptor (RET). The VEGF receptors and PDGFRβ are important in angiogenesis.
T
ThrombocytopeniaThrombocytopenia (or -paenia, or thrombopenia in short) is the presence of relatively few platelets in blood. Platelets help form clots to prevent excessive bleeding. See Wikipedia article.
Tumor suppressor geneA gene involved in regulating cell growth which, when mutated (inactivated) contribute to cancer development. (See also:oncogene).
TyrosineOne of the twenty amino acid building blocks of proteins.
Tyrosine kinasesEnzymes which catalyze phosphorylation of tyrosine residues in proteins, often leading to activation of the protein/enzyme.
U
UltrasoundA radiological technique using very high frequency sound waves (about 5 MHz) for imaging internal organs. The signal is emitted from a transducer placed in contact with the skin and is reflected back, detected, and used to form the image.
UnresectableNot amenable to surgical removal.

The Life Raft Group would like to thank Dr. David Josephy – University of Guelph for his hard work on this glossary.

Next Steps

Doctor’s  Visit Checklist, a Beginning Your GIST Education Info Sheet, and more are available in Newly Diagnosed & the Patient Resource Toolkit

Join Now and connect with the Patient Registry Team at The LRG, and other patients & caregivers on the ListServ

Be a part of the cure by donating to the GIST Collaborative Tissue Bank

Core Values