An Immunohistochemical study of the origin and differentiation of gastric stromal tumor.

Background : Gastrointestinal stromal tumors (GISTs) have the subject of debate and controversy regarding their histogenesis, criteria on malignancy, prognostic features, site-specificity and their nomenclature. These tumors have various phenotypical features and are generally divided into (1) tumors showing differentiation toward smooth muscle cells (2) tumors showing apparent differentiation toward neural elements (3) tumors showing dual differentiation toward smooth muscle and neural elements (4) tumors lacking differentiation toward either cell type (uncommitted type). This study was performed to identify the possible origin and differentiation of gastric stromal tumor. Methods : This study was performed on 38 patients who had gastric stromal tumors on endoscopy or endoscopic ultrasonography and confirmed by endoscopic or surgical resection between January 1994 and June 1999 at Department of Internal Medicine, Korea University College of Medicine. Formalin-fixed, paraffin-embedded tissues were studied by immunohistochemical method for detecting the presence of CD 34, CD 117, Vimentin, SMA, Desmin, S-100, PGP 9.5 and NSE. Results : The patients' age ranged from 26 to 81 years old, with an average age of 53.8 years. The male to female ratio was 1:1.2. Endoscopic resections were performed on 22 patients and surgical operations on 16 patients. The average tumor size was 25.3 mm in diameter. On immunohistochemical staining method, the uncommitted type was found in 18 patients (47.4%), of which 17 patients (94.4%) were CD117 (+), CD34 (+), Vimentin (+), 12 patients (31.6%) had musculardifferentiation, 7 patients (18.4%) showed neural differentiation and 1 patient (2.6%) showed differentiation toward both neural and muscular immunohistochemical pattern. Conclusion : Gastric stromal tumors showed phenotypical diversity in immunohistochemical staining suggesting different histogenesis. Most uncommitted type had a phenotype of intersititial cells of Cajal (ICC) and this evidence supports the hypothesis that uncommitted type has the origin of ICC.