Prevalence in 1819 predominantly male patients who received colonoscopy for screening with indo carmine spray technique was 9.35% accounting for 15% of neoplastic lesions (Soetikno).
The likelihood that such flat or depressed lesions harbor in-situ or submucosal carcinoma is more than 5 times higher than the rate of polypoid lesions after adjusting for polyp size.
Several studies have been done with baseline colonoscopy and repeated exams within 2-5 years to detect interval neoplasia found 0.3% to 0.9% of patients have interval cancers within only a few years after colonoscopy and polypectomy.
Explanations that lesions can appear in the short amount of time explained by new de novo lesions, rapidly growing lesions, missed lesions, or incompletely removed lesions that can account for these interval cancers.
Chemoendoscopy with special stains or narrow band imaging or fluorescence endoscopy may help visualize and demarcate flat lesions at colonoscopy.