[Gastrointestinal stromal tumors (GIST) of the stomach as a cause of upper gastrointestinal bleeding]

Abstract

Gastrointestinal stromal tumors (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. GIST is currently defined as a gastrointestinal tract mesenchymal tumor containing spindle cells (less commonly epitheloid cells or rarely both) and showing CD 117 (c-kit protein) positivity in more than 95% of cases. Although they may arise throughout the gut, the commonest site are stomach (60-70%), small intestine (20-30%), colorectum (5%) and esophagus (up to 5%). Rarely, GISTs develop in the retroperitoneum, omentum or mesentery. GIST originates from the intestinal cell of Cajal (ICC). ICCs are located in and around the myenteric plexus and are thought to function as intestinal pacemaker cells. Historicaly, GIST were often misclassified as leiomyomas or leiomyosarcomas. Subsequently, it has been determined that GISTs have distinct ultrastructural features and immunophenotypical markers compared with smooth muscle and smooth muscle tumors. GIST predominantly occur in middle aged and older patients, with no significant difference in the sex incidence. Data from the recent population study suggest an incidence of about 10-22 cases per million persons per year. Clinical presentation of GIST varies widely, and depends on tumor size and location. GISTs that caused symptoms tended to be larger with an average size of 6cm versus 2cm for asymptomatic GISTs. Symptoms are most commonly related to mass effect or bleeding. GISTs can grow very large before producing symptoms. Commonest symptom of gastric GIST is manifest or occult bleeding. Abudant, life-threateting bleeding that require urgent surgery is rare. For patient with primary, localized, nonmetastatic GIST, complete surgical resection represents the only chance for cure. Lymhadenectomy is not necessary, because lymph node metastasis is very rare. The 5 year survival rate in patients with resected primary GISTs ranges from 48-65%. Conventional chemotherapy and radiation therapy is ineffective in the treatment of GIST. Imatinib mesilate (a tyrosine kinase inhibitor) was confirmed to be effective against metastatic or unresectable GISTs.