Gastric Schwannoma: The Masquerader amongst Gastric Mesenchymal Tumours

Abstract

Introduction: Gastric Schwannoma (GS) is a rare gastrointestinal mesenchymal tumour and needs to be distinguished from other common mesenchymal tumours like Gastrointestinal Stromal Tumour (GIST). GS is composed of Antoni A areas with peritumoural lymphoid cuff unlike conventional schwannomas. GS are difficult to differentiate from other mesenchymal submucosal tumours like GIST. The histological features and strong positive immunostaining for S100 protein along with CD117 (Cluster of Differentiation) and Discovered on GIST 1 (DOG1) immunonegativity is required to confirm the diagnosis. Aim: To analyse the histopathological, immunohistochemical, radiological characteristics and follow-up data of GS. Materials and Methods: This was a retrospective descriptive study conducted in a tertiary care hospital in Southern India. There was a total of eight cases of GS retrieved from the Pathology archives from January 2010 to December 2019. The clinical information along with radiology reports were retrieved from the electronic database. The retrieved slides were analysedfor clinicopathological features. The descriptive analysis of the data was done, and the results were presented as mean, frequencies, and percentages. Results: All eight cases of GS presented in the fifth to eighth decade of life with a female preponderance (male to female ratio of 1:3). Six out of eight cases were symptomatic (75%). Radiologically, a differential diagnosis of GIST was considered in all 8 cases (100%). Microscopically, all 8 cases (100%) exhibited fascicles of spindle cells with mild nuclear pleomorphism, prominent peritumoural lymphoid cuff, and few secondary changes. S100 immunohistochemistry was done in six cases of GS and all showed diffuse strong positivity. The remaining two cases were positive for SRY-related High Mobility Group (HMG)-box 10 (SOX). Conclusion: Preoperative diagnosis of GS is difficult due to non-specific endoscopic or radiological findings. In gastric submucosal tumours, GS should be considered as one of the differential diagnosis. The histopathological and immunohistochemical features are considered the gold standard to diagnose GS.