7063 An immunohistochemical study of the origin and differentiation of gastric stromal tumor.

Abstract

Objective: Gastrointestinal stromal tumors(GISTs), formerly known as leiomyomas and leiomyosarcomas, are the subject of much debate and controversy regarding their histogenesis, criteria of diagnosis, prognostic features, and 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). Some authors use the term GIST in a more restricted sense, i.e. only for the uncommitted type. This study was performed to identify a possible origin and differentiation of gastric stromal tumor. Methods: An immunohistochemical staining was performed on 38 patients who were suspected to have gastric stromal tumors on gastroscopy or endoscopic ultrasonography and who were confirmed by endoscopic resection or operation between January 1994 and June 1999 at Department of Internal Medicine, Institute Digestive Disease and Nutrition, Korea University College of Medicine. Formalin-fixed, paraffinembedded tissues from 38 patinets were immunostained for CD 34, CD 117, Vimentin, SMA, Desmin, S-100, PGP 9.5, and NSE. Results: The patients' age ranged from 26 to 81, with an average age of 53.8 years. The male to female ratio was 12:26. Endoscopic resections were performed on 22 patients and operations on 16 patients. The average tumor size was 25.3mm. On immunohistochemical staining, uncommitted type was found in 18 patients(47.4%), of which 17 patients(94.4%) were CD117(+) CD34(+)Vimentin(+), a phenotype consistent with a interstitial cells of Cajal(ICC). 12 patients(31.6%) were thought to have muscular differentiation with SMA(+)S-100(-), 7 patients(18.4%) showed neural differentiation with S-100(+)PGP(+)NSE(+)Vimentin(+)SMA(-), and 1 patient(2.6%) showed dual differentiation with S-100(+)PGP (+)NSE (+)Vimentin (+)SMA(+). Conclusion: Of the 38 gastric stromal tumors, there were 12 patients with muscular differentiation, 7 patients with neural differentiation, 1 patient with dual differentiation, and 18 patients with uncommitted type. Most of uncommitted type had a phenotype of ICC, and this supports the hypothesis that uncommitted type has a origin of ICC.