Risk Stratification of Patients with Gastrointestinal Stromal Tumours by Histopathological and Immunuhistochemical Analysis

Abstract

Introduction: Gastrointestinal Stromal Tumours (GISTs) are the most common mesenchymal tumours of the alimentary canal. Interstitial cells of Cajal are believed to be the cell of origin of GIST which regulates gastrointestinal peristalsis. GISTs encompass a clinicopathologically distinctive, but heterogenous group of neoplasms with reference to their origin, cellular differentiation and prognosis. Aim: The aim of this study was to analyse the histopathological and immunohistochemical characteristics of GIST. Materials and Methods: A hospital-based cross-sectional study of 108 cases of GIST were studied over a period of three years from January, 2017 to December, 2019 in Department of Pathology, Vydehi Institute of Medical Sciences and Research Institute (VIMS&RC), Bangalore. Patient’s demographic data like age and gender were collected. Tumour characteristics like site, size and number of lesions were analysed. Histopathological and immunohistochemistry for Desmin, CD117 and DOG-1 were analysed for significant association with risk groups. Risk stratification according to the Fletcher's risk classification, the cases were divided was divided into very low, low, intermediate and high risk groups. The master chart of collected data was prepared in Excel sheet. Chi-square test with Yates correction was used to calculate p-value to ascertain statistical significance. The master chart of collected data was prepared in Excel sheet. Descriptive statistical analysis was presented in the form of tables, figures and diagrams wherever necessary using Epi info 07 statistical software package. Results: The mean age of the patients was 55.6±14.4 years. Males (55.6%/60 cases) were commonly affected than females (44.4%/48 cases). Small intestine was the commonest location (44.4%/48 cases). Tumour size ranged from 1.5 cm to 25 cm with a mean of 9.1 cm. Microscopic findings revealed that spindle cell type was the most common (86.1%/93 cases). Majority of the cases belonged to high risk category. Multifocality, necrosis, tumour size and >5 mitosis/50 High Power Field (HPF) showed significant association with high risk category tumours (p-value 0.033, 0.016, 0.004 and <0.001, respectively). Immunohistochemical staining showed positivity for CD 117 (83.3%/90 cases), DOG-1 (88.9%/96 cases) and 108 cases/100% negativity for desmin. Conclusion: This study found significant association of high risk groups with tumour size, multifocality, necrosis and mitosis >5/50 HPF. Risk categorisation of GIST remains important. A combination of CD117 and DOG-1 will be more useful in diagnosing GIST rather than using them alone.