A 61-year-old asymptomatic man underwent colonoscopy during a medical check-up, which revealed multiple translucent submucosal tumor-like lesions along the ascending and transverse colon along with erythematous areas (Fig. 1A). Computed tomography (CT) colonography revealed multiple air-containing cysts within the walls of the colon (Fig. 1B, C). Clostridioides difficile toxin was not detected in stools. We performed biopsies of the cystic lesions. Histopathological examination revealed edematous and mild non-specific inflammatory cell infiltration (Fig. 2A).