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==Pathophysiology==
==Pathophysiology==
On microscopic histopathological analysis, spindle cells or plump epithelioid cells are characteristic findings of gastrointestinal stromal tumor.
Gastrointestinal stromal tumors (GISTs) are rare but the most common [[mesenchymal]] (nonepithelial) [[tumors]] of the gastrointestinal tract. GISTs are derived from the [[interstitial cells of Cajal]] or undifferentiated [[precursor]] cells that finally develop into [[interstitial cells of Cajal]]. GIST tumors can either be [[benign]] tumors or massive [[malignant]] tumors with widespread [[metastasis]]. They can occur in any part of the [[gastrointestinal tract]] with the most common location as [[stomach]]. GIST ([[tumors]]) can grow as an endophytic or exophytic lesions. [[Genes]] involved in the pathogenesis of gastrointestinal stromal tumors include [[mutations]] in c-Kit gene and PDGFRA (platelet derived growth factor receptor-alpha) gene. Both Kit gene and PDGFRA are [[tyrosine kinase]] receptors and control [[cell proliferation]]. [[Mutation]] in c-Kit gene and PDGFRA  leads to  inhibition of [[apoptosis]] and uncontrolled [[cell proliferation]]. In some rare cases where the patient do not exhibit the typical [[mutation]] in c-Kit and PDGFRA, [[mutation|mutations]] in [[succinate dehydrogenase]] (SDH) have been reported. Conditions associated with GIST include [[urticaria pigmentosa]], [[neurofibromatosis type 1]], and Carney-Stratakis syndrome. On [[gross pathology]], GISTs  have a rounded appearance with areas of [[hemorrhage]]. On [[microscopic]] [[histopathological]] [[analysis]], GISTs are cellular [[tumor|tumors]] arising from muscularis propria and composed of [[spindle cells]] (70%), [[Epithelioid cell|epithelioid cells]] (20%) or either one of them.


==Causes==
==Causes==

Revision as of 19:41, 18 December 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Parminder Dhingra, M.D. [2]

Overview

In medical oncology, gastrointestinal stromal tumors (GIST) are a rare tumor of the gastrointestinal tract. GIST is a form of connective tissue cancer, or sarcoma. GISTs are therefore non-epithelial tumors, separate from more common forms of bowel cancer. Majority of the cases occur in the stomach(70%), 20% of cases in the small intestine and less than 10% in the esophagus. Small tumors are generally benign, especially when cell division rate is slow, but large tumors disseminate to the liver, omentum and peritoneal cavity. They rarely occur in other abdominal organs. Gastrointestinal stromal tumor affects men and women equally.

Historical Perspective

Prior to the advent and use of electron microscopy, gastrointestinal stromal tumors (GIST) were classified as smooth muscle tumors such as leiomyomas or leiomyosarcomas. In 1983, Mazur and Clark and Schaldenbrand and Appleman in 1984 were the first to describe gastrointestinal stromal tumors as an independent entity of intra-abdominal tumors that were neither carcinomas nor exhibit histologic features of smooth muscle or nerve cells. In 1998, Kindblom et al described the origin of GIST as pluripotential mesenchymal stem cells which were programmed to differentiate into the interstitial cell of Cajal. In 1998 Hirota and others were the first to describe c-kit (proto-oncogene) mutations as the cause of GIST. In 2001, Joensuu was the first to report successful treatment of patients with advanced GIST on molecular-targeted therapy (imatinib).

Pathophysiology

Gastrointestinal stromal tumors (GISTs) are rare but the most common mesenchymal (nonepithelial) tumors of the gastrointestinal tract. GISTs are derived from the interstitial cells of Cajal or undifferentiated precursor cells that finally develop into interstitial cells of Cajal. GIST tumors can either be benign tumors or massive malignant tumors with widespread metastasis. They can occur in any part of the gastrointestinal tract with the most common location as stomach. GIST (tumors) can grow as an endophytic or exophytic lesions. Genes involved in the pathogenesis of gastrointestinal stromal tumors include mutations in c-Kit gene and PDGFRA (platelet derived growth factor receptor-alpha) gene. Both Kit gene and PDGFRA are tyrosine kinase receptors and control cell proliferation. Mutation in c-Kit gene and PDGFRA leads to inhibition of apoptosis and uncontrolled cell proliferation. In some rare cases where the patient do not exhibit the typical mutation in c-Kit and PDGFRA, mutations in succinate dehydrogenase (SDH) have been reported. Conditions associated with GIST include urticaria pigmentosa, neurofibromatosis type 1, and Carney-Stratakis syndrome. On gross pathology, GISTs have a rounded appearance with areas of hemorrhage. On microscopic histopathological analysis, GISTs are cellular tumors arising from muscularis propria and composed of spindle cells (70%), epithelioid cells (20%) or either one of them.

Causes

There are no established causes for gastrointestinal stromal tumor.

Epidemiology and Demographics

Gastrointestinal stromal tumor affects men and women equally.

Risk factors

The most potent risk factor in the development of GISTs are age 50-80 and certain genetic syndromes like neurofibromatosis type 1, Carney-Stratakis syndrome and familial gastrointestinal stromal tumor syndrome.

Screening

Differential Diagnosis

Gastrointestinal stromal tumor must be differentiated from gastrointestinal leiomyoma, gastrointestinal leiomyosarcoma, gastrointestinal lymphoma / gastric lymphoma, gastrointestinal schwannoma and gastrointestinal carcinoid.

Natural History, Complications and Prognosis

Most common site of involvement of GIST is stomach(70%).

Staging

According to the American Joint Committee on Cancer, there are 4 stages of gastrointestinal stromal tumor based on the tumor spread.

History and Symptoms

Symptoms of gastrointestinal stromal tumor include dysphagia, gastrointestinal hemorrhage, and vague abdominal pain.

Physical Examination

Laboratory Examination

Abdominal X-ray

On abdominal X-ray, gastrointestinal stromal tumor is characterized by soft tissue density displacing bowel loops.

CT scan

Abdominal CT scan may be helpful in the diagnosis of gastrointestinal stromal tumor.

MRI

MRI scan may be helpful in the diagnosis of gastrointestinal stromal tumor.

Ultrasound

Other Imaging Findings

Fluoroscopy may be helpful in the diagnosis of gastrointestinal stromal tumor.

Other Diagnostic studies

Medical Therapy

The predominant therapy for gastrointestinal stromal tumor is surgical resection. Adjunctive chemotherapy/tyrosine Kinase Inhibitor therapy may be required.

Surgical Therapy

The predominant therapy for gastrointestinal stromal tumor is surgical resection. Adjunctive chemotherapy/tyrosine Kinase Inhibitor therapy may be required.

Prevention

References


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