Immune checkpoint inhibitor-induced diarrhea/colitis: Endoscopic and pathologic findings

Table 1 Summary of endoscopic and pathological findings of immune-related diarrhea and colitis

Endoscopic and pathological findings of immune-related diarrhea and colitis
Endoscopic findings
Endoscopic features	(1) Exudates; (2) loss of vascular pattern; (3) granular or edematous mucosa; (4) patch or diffuse erythema; (5) aphtha; (6) ulceration
Inflammatory distribution	(1) Diffuse; (2) patchy (dominantly more diffuse than patchy)
Risk factors for steroid-refractory colitis	(1) Extensively inflamed area (e.g., pancolitis); (2) deeper ulceration
Pathological findings
Anti-CTLA-4 associated colitis	Like autoimmune colitis: (1) lamina propria expansion due to dense lymphoplasmacytic infiltrate; (2) increased intraepithelial lymphocytosis; (3) apoptosis in the crypts; (4) neutrophilic cryptitis and crypt abscess; (5) occasional prominent eosinophilia in the lamina propria; (6) the lack of findings of basal plasmacytosis, crypt distortion, or granulomas
Anti-PD1/anti-PDL1-associated colitis	(1) Expansion of lamina propria by lymphoplasmacytic infiltrate; (2) the increase in intraepithelial neutrophils and neutrophilic crypt abscess; (3) crypt distortion; (4) increased crypt cell apoptosis

CTLA-4: Cytotoxic T-lymphocyte antigen-4; PD1: Programmed cell death protein 1; PDL1: Programmed cell death receptor ligand 1.