SMN1 and mesenchymal cell neoplasm: IHC is used to differentiate gastric schwannoma from other GI mesenchymal tumors; gastric schwannoma strongly and diffusely stains positive for S100, vimentin, and glial fibrillary acidic protein (GFA) and is consistently negative for CD117, DOG -1, CD 34 and smooth muscle actin (SMA).