Gastrointestinal Stromal Tumors: All tumors in the GASTROINTESTINAL TRACT arising from mesenchymal cells (MESODERM) except those of smooth muscle cells (LEIOMYOMA) or Schwann cells (SCHWANNOMA).Proto-Oncogene Proteins c-kit: A protein-tyrosine kinase receptor that is specific for STEM CELL FACTOR. This interaction is crucial for the development of hematopoietic, gonadal, and pigment stem cells. Genetic mutations that disrupt the expression of PROTO-ONCOGENE PROTEINS C-KIT are associated with PIEBALDISM, while overexpression or constitutive activation of the c-kit protein-tyrosine kinase is associated with tumorigenesis.Gastrointestinal Neoplasms: Tumors or cancer of the GASTROINTESTINAL TRACT, from the MOUTH to the ANAL CANAL.Benzamides: BENZOIC ACID amides.PiperazinesPyrimidines: A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (CYTOSINE; THYMINE; and URACIL) and form the basic structure of the barbiturates.Receptor, Platelet-Derived Growth Factor alpha: A PDGF receptor that binds specifically to both PDGF-A chains and PDGF-B chains. It contains a protein-tyrosine kinase activity that is involved in SIGNAL TRANSDUCTION.Stromal Cells: Connective tissue cells of an organ found in the loose connective tissue. These are most often associated with the uterine mucosa and the ovary as well as the hematopoietic system and elsewhere.Antineoplastic Agents: Substances that inhibit or prevent the proliferation of NEOPLASMS.Mesenchymoma: A mixed mesenchymal tumor composed of two or more mesodermal cellular elements not commonly associated, not counting fibrous tissue as one of the elements. Mesenchymomas are widely distributed in the body and about 75% are malignant. (Dorland, 27th ed; Holland et al., Cancer Medicine, 3d ed, p1866)Neoplasms, Connective Tissue: Neoplasms composed of connective tissue, including elastic, mucous, reticular, osseous, and cartilaginous tissue. The concept does not refer to neoplasms located in connective tissue.Epithelioid Cells: Characteristic cells of granulomatous hypersensitivity. They appear as large, flattened cells with increased endoplasmic reticulum. They are believed to be activated macrophages that have differentiated as a result of prolonged antigenic stimulation. Further differentiation or fusion of epithelioid cells is thought to produce multinucleated giant cells (GIANT CELLS).Mitotic Index: An expression of the number of mitoses found in a stated number of cells.Pyrroles: Azoles of one NITROGEN and two double bonds that have aromatic chemical properties.Duodenal Neoplasms: Tumors or cancer of the DUODENUM.Leiomyosarcoma: A sarcoma containing large spindle cells of smooth muscle. Although it rarely occurs in soft tissue, it is common in the viscera. It is the most common soft tissue sarcoma of the gastrointestinal tract and uterus. The median age of patients is 60 years. (From Dorland, 27th ed; Holland et al., Cancer Medicine, 3d ed, p1865)Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Ileal Neoplasms: Tumors or cancer in the ILEUM region of the small intestine (INTESTINE, SMALL).Jejunal Neoplasms: Tumors or cancer in the JEJUNUM region of the small intestine (INTESTINE, SMALL).Neoplasms, Multiple Primary: Two or more abnormal growths of tissue occurring simultaneously and presumed to be of separate origin. The neoplasms may be histologically the same or different, and may be found in the same or different sites.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Intestinal Neoplasms: Tumors or cancer of the INTESTINES.Tumor Markers, Biological: Molecular products metabolized and secreted by neoplastic tissue and characterized biochemically in cells or body fluids. They are indicators of tumor stage and grade as well as useful for monitoring responses to treatment and predicting recurrence. Many chemical groups are represented including hormones, antigens, amino and nucleic acids, enzymes, polyamines, and specific cell membrane proteins and lipids.Indoles: Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.Sex Cord-Gonadal Stromal Tumors: Neoplasms derived from the primitive sex cord or gonadal stromal cells of the embryonic GONADS. They are classified by their presumed histogenesis and differentiation. From the sex cord, there are SERTOLI CELL TUMOR and GRANULOSA CELL TUMOR; from the gonadal stroma, LEYDIG CELL TUMOR and THECOMA. These tumors may be identified in either the OVARY or the TESTIS.Protein Kinase Inhibitors: Agents that inhibit PROTEIN KINASES.Stomach Neoplasms: Tumors or cancer of the STOMACH.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Digestive System Surgical Procedures: Surgery performed on the digestive system or its parts.DNA Mutational Analysis: Biochemical identification of mutational changes in a nucleotide sequence.Neurofibromatosis 1: An autosomal dominant inherited disorder (with a high frequency of spontaneous mutations) that features developmental changes in the nervous system, muscles, bones, and skin, most notably in tissue derived from the embryonic NEURAL CREST. Multiple hyperpigmented skin lesions and subcutaneous tumors are the hallmark of this disease. Peripheral and central nervous system neoplasms occur frequently, especially OPTIC NERVE GLIOMA and NEUROFIBROSARCOMA. NF1 is caused by mutations which inactivate the NF1 gene (GENES, NEUROFIBROMATOSIS 1) on chromosome 17q. The incidence of learning disabilities is also elevated in this condition. (From Adams et al., Principles of Neurology, 6th ed, pp1014-18) There is overlap of clinical features with NOONAN SYNDROME in a syndrome called neurofibromatosis-Noonan syndrome. Both the PTPN11 and NF1 gene products are involved in the SIGNAL TRANSDUCTION pathway of Ras (RAS PROTEINS).Sarcoma: A connective tissue neoplasm formed by proliferation of mesodermal cells; it is usually highly malignant.Prognosis: A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.Carney Complex: Autosomal dominant syndrome characterized by cardiac and cutaneous MYXOMAS; LENTIGINOSIS (spotty pigmentation of the skin), and endocrinopathy and its associated endocrine tumors. The cardiac myxomas may lead to SUDDEN CARDIAC DEATH and other complications in Carney complex patients. The gene coding for the PRKAR1A protein is one of the causative genetic loci (type 1). A second locus is at chromosome 2p16 (type 2).Gastrectomy: Excision of the whole (total gastrectomy) or part (subtotal gastrectomy, partial gastrectomy, gastric resection) of the stomach. (Dorland, 28th ed)Leiomyoma: A benign tumor derived from smooth muscle tissue, also known as a fibroid tumor. They rarely occur outside of the UTERUS and the GASTROINTESTINAL TRACT but can occur in the SKIN and SUBCUTANEOUS TISSUE, probably arising from the smooth muscle of small blood vessels in these tissues.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Antigens, CD34: Glycoproteins found on immature hematopoietic cells and endothelial cells. They are the only molecules to date whose expression within the blood system is restricted to a small number of progenitor cells in the bone marrow.Drug Resistance, Neoplasm: Resistance or diminished response of a neoplasm to an antineoplastic agent in humans, animals, or cell or tissue cultures.Interstitial Cells of Cajal: c-Kit positive cells related to SMOOTH MUSCLE CELLS that are intercalated between the autonomic nerves and the effector smooth muscle cells of the GASTROINTESTINAL TRACT. Different phenotypic classes play roles as pacemakers, mediators of neural inputs, and mechanosensors.Endosonography: Ultrasonography of internal organs using an ultrasound transducer sometimes mounted on a fiberoptic endoscope. In endosonography the transducer converts electronic signals into acoustic pulses or continuous waves and acts also as a receiver to detect reflected pulses from within the organ. An audiovisual-electronic interface converts the detected or processed echo signals, which pass through the electronics of the instrument, into a form that the technologist can evaluate. The procedure should not be confused with ENDOSCOPY which employs a special instrument called an endoscope. The "endo-" of endosonography refers to the examination of tissue within hollow organs, with reference to the usual ultrasonography procedure which is performed externally or transcutaneously.Exons: The parts of a transcript of a split GENE remaining after the INTRONS are removed. They are spliced together to become a MESSENGER RNA or other functional RNA.Disease-Free Survival: Period after successful treatment in which there is no appearance of the symptoms or effects of the disease.Laparotomy: Incision into the side of the abdomen between the ribs and pelvis.Neurilemmoma: A neoplasm that arises from SCHWANN CELLS of the cranial, peripheral, and autonomic nerves. Clinically, these tumors may present as a cranial neuropathy, abdominal or soft tissue mass, intracranial lesion, or with spinal cord compression. Histologically, these tumors are encapsulated, highly vascular, and composed of a homogenous pattern of biphasic fusiform-shaped cells that may have a palisaded appearance. (From DeVita Jr et al., Cancer: Principles and Practice of Oncology, 5th ed, pp964-5)Tumor Burden: The total amount (cell number, weight, size or volume) of tumor cells or tissue in the body.Somatostatinoma: A SOMATOSTATIN-secreting tumor derived from the pancreatic delta cells (SOMATOSTATIN-SECRETING CELLS). It is also found in the INTESTINE. Somatostatinomas are associated with DIABETES MELLITUS; CHOLELITHIASIS; STEATORRHEA; and HYPOCHLORHYDRIA. The majority of somatostatinomas have the potential for METASTASIS.Cell Line, Tumor: A cell line derived from cultured tumor cells.Protein-Tyrosine Kinases: Protein kinases that catalyze the PHOSPHORYLATION of TYROSINE residues in proteins with ATP or other nucleotides as phosphate donors.S100 Proteins: A family of highly acidic calcium-binding proteins found in large concentration in the brain and believed to be glial in origin. They are also found in other organs in the body. They have in common the EF-hand motif (EF HAND MOTIFS) found on a number of calcium binding proteins. The name of this family derives from the property of being soluble in a 100% saturated ammonium sulfate solution.Leiomyoma, Epithelioid: A relatively rare smooth muscle tumor found most frequently in the wall of the gastrointestinal tract, especially in the stomach. It is similar to other smooth muscle tumors but may become very large and hemorrhage and exhibit small cystic areas. Simple excision is almost always curative. (From Dorland, 27th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1354)Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Gastroscopy: Endoscopic examination, therapy or surgery of the interior of the stomach.Positron-Emission Tomography: An imaging technique using compounds labelled with short-lived positron-emitting radionuclides (such as carbon-11, nitrogen-13, oxygen-15 and fluorine-18) to measure cell metabolism. It has been useful in study of soft tissues such as CANCER; CARDIOVASCULAR SYSTEM; and brain. SINGLE-PHOTON EMISSION-COMPUTED TOMOGRAPHY is closely related to positron emission tomography, but uses isotopes with longer half-lives and resolution is lower.Peritoneal Neoplasms: Tumors or cancer of the PERITONEUM.Disease Progression: The worsening of a disease over time. This concept is most often used for chronic and incurable diseases where the stage of the disease is an important determinant of therapy and prognosis.Endoscopy, Gastrointestinal: Endoscopic examination, therapy or surgery of the gastrointestinal tract.Electron Transport Complex II: A flavoprotein oxidase complex that contains iron-sulfur centers. It catalyzes the oxidation of SUCCINATE to fumarate and couples the reaction to the reduction of UBIQUINONE to ubiquinol.Double-Balloon Enteroscopy: Endoscopy of the small intestines accomplished while advancing the endoscope into the intestines from the stomach by alternating the inflation of two balloons, one on an innertube of the endoscope and the other on an overtube.Omentum: A double-layered fold of peritoneum that attaches the STOMACH to other organs in the ABDOMINAL CAVITY.Pelvic Neoplasms: Tumors or cancer of the pelvic region.Neurofibrosarcoma: A malignant tumor that arises from small cutaneous nerves, is locally aggressive, and has a potential for metastasis. Characteristic histopathologic features include proliferating atypical spindle cells with slender wavy and pointed nuclei, hypocellular areas, and areas featuring organized whorls of fibroblastic proliferation. The most common primary sites are the extremities, retroperitoneum, and trunk. These tumors tend to present in childhood, often in association with NEUROFIBROMATOSIS 1. (From DeVita et al., Cancer: Principles & Practice of Oncology, 5th ed, p1662; Mayo Clin Proc 1990 Feb;65(2):164-72)Incidental Findings: Unanticipated information discovered in the course of testing or medical care. Used in discussions of information that may have social or psychological consequences, such as when it is learned that a child's biological father is someone other than the putative father, or that a person tested for one disease or disorder has, or is at risk for, something else.Ki-67 Antigen: A CELL CYCLE and tumor growth marker which can be readily detected using IMMUNOCYTOCHEMISTRY methods. Ki-67 is a nuclear antigen present only in the nuclei of cycling cells.Neoplasm Metastasis: The transfer of a neoplasm from one organ or part of the body to another remote from the primary site.Soft Tissue Neoplasms: Neoplasms of whatever cell type or origin, occurring in the extraskeletal connective tissue framework of the body including the organs of locomotion and their various component structures, such as nerves, blood vessels, lymphatics, etc.Intestine, Small: The portion of the GASTROINTESTINAL TRACT between the PYLORUS of the STOMACH and the ILEOCECAL VALVE of the LARGE INTESTINE. It is divisible into three portions: the DUODENUM, the JEJUNUM, and the ILEUM.Gastrointestinal Hemorrhage: Bleeding in any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM.Succinate Dehydrogenase: A flavoprotein containing oxidoreductase that catalyzes the dehydrogenation of SUCCINATE to fumarate. In most eukaryotic organisms this enzyme is a component of mitochondrial electron transport complex II.Hemoperitoneum: Accumulations of blood in the PERITONEAL CAVITY due to internal HEMORRHAGE.Neoadjuvant Therapy: Preliminary cancer therapy (chemotherapy, radiation therapy, hormone/endocrine therapy, immunotherapy, hyperthermia, etc.) that precedes a necessary second modality of treatment.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.DNA, Neoplasm: DNA present in neoplastic tissue.Biopsy, Needle: Removal and examination of tissue obtained through a transdermal needle inserted into the specific region, organ, or tissue being analyzed.Liver Neoplasms: Tumors or cancer of the LIVER.Gene Expression Regulation, Neoplastic: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in neoplastic tissue.Lethargy: A general state of sluggishness, listless, or uninterested, with being tired, and having difficulty concentrating and doing simple tasks. It may be related to DEPRESSION or DRUG ADDICTION.Meckel Diverticulum: A congenital abnormality characterized by the outpouching or sac formation in the ILEUM. It is a remnant of the embryonic YOLK SAC in which the VITELLINE DUCT failed to close.Neoplasm Proteins: Proteins whose abnormal expression (gain or loss) are associated with the development, growth, or progression of NEOPLASMS. Some neoplasm proteins are tumor antigens (ANTIGENS, NEOPLASM), i.e. they induce an immune reaction to their tumor. Many neoplasm proteins have been characterized and are used as tumor markers (BIOMARKERS, TUMOR) when they are detectable in cells and body fluids as monitors for the presence or growth of tumors. Abnormal expression of ONCOGENE PROTEINS is involved in neoplastic transformation, whereas the loss of expression of TUMOR SUPPRESSOR PROTEINS is involved with the loss of growth control and progression of the neoplasm.Endometrial Stromal Tumors: Neoplasms of the endometrial stroma that sometimes involve the MYOMETRIUM. These tumors contain cells that may closely or remotely resemble the normal stromal cells. Endometrial stromal neoplasms are divided into three categories: (1) benign stromal nodules; (2) low-grade stromal sarcoma, or endolymphatic stromal myosis; and (3) malignant endometrial stromal sarcoma (SARCOMA, ENDOMETRIAL STROMAL).Survival Rate: The proportion of survivors in a group, e.g., of patients, studied and followed over a period, or the proportion of persons in a specified group alive at the beginning of a time interval who survive to the end of the interval. It is often studied using life table methods.Neoplasm Recurrence, Local: The local recurrence of a neoplasm following treatment. It arises from microscopic cells of the original neoplasm that have escaped therapeutic intervention and later become clinically visible at the original site.Neoplasm Staging: Methods which attempt to express in replicable terms the extent of the neoplasm in the patient.Kaplan-Meier Estimate: A nonparametric method of compiling LIFE TABLES or survival tables. It combines calculated probabilities of survival and estimates to allow for observations occurring beyond a measurement threshold, which are assumed to occur randomly. Time intervals are defined as ending each time an event occurs and are therefore unequal. (From Last, A Dictionary of Epidemiology, 1995)Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Cecal Neoplasms: Tumors or cancer of the CECUM.