Gastric Crohn’s disease presenting as a subepithelial tumor: A case report

Table 1 Immunohistochemistryguided differential diagnosis of a gastric subepithelial lesion in the presented case

Entity	Prototypical IHC profile	Findings in the presented case	Interpretation
GIST	KIT (CD117)+, DOG1+, often CD34+	KIT (CD117)-, DOG1-, CD34-	Effectively rules out GIST
Gastrointestinal schwannoma	Diffuse S100+ (± SOX10+); CD34 usually negative	Focal S100 positivity; SOX10 staining not performed	Not supportive of schwannoma
IFP	CD34+; KIT (CD117)/DOG1-; may harbor PDGFRA mutation	CD34-	Argues against IFP
GCT	Diffuse S100+; SOX10+; CD68+ in tumor cells	Focal S100 positivity; CD68 highlights non-neoplastic histiocytes	Pattern not compatible with GCT
Leiomyoma	SMA+, desmin+, hcaldesmon+; KIT (CD117)/DOG1-	No features of a smooth muscle tumor; SMA/desmin staining not performed	Unlikely
LCH	CD1a+, Langerin (CD207)+, S100+	CD1a-; Langerin (CD207) staining not performed; focal S100 positivity	Rules out LCH
Upper gastrointestinal Crohn’s disease	Noncaseating granulomas; CD68+ histiocytes; typically CD1a-	Chronic active gastritis with ulceration and noncaseating granulomas; CD68+ histiocytes; CD1a-	Favored diagnosis

IHC: Immunohistochemistry; GIST: Gastrointestinal stromal tumor; IFP: Inflammatory fibroid polyp; GCT: Granular cell tumor; LCH: Langerhans cell histiocytosis.