Risk factors of traditional serrated adenoma and clinicopathologic characteristics of synchronous conventional adenoma

Background and Aims: Traditional serrated adenoma (TSA) is rare and known to have a malignant potential. We aimed to investigate the prevalence and risk factors of TSA and compare the characteristics of synchronous conventional adenoma (AD) in patients with TSA with those of AD in patients with AD only. Methods: We reviewed medical records of 31,932 healthy subjects who underwent screening colonoscopy at a single hospital between 2012 and 2017. Results: TSA was observed in 116 patients (.4%). Among them, 47 patients (40.5%) had TSA only and 69 patients (59.5%) had synchronous AD. Multivariable analysis showed independent risk factors for TSA to include age >= 50 years (odds ratio [OR], 3.34; 95% confidence interval [CI], 1.72-6.49; P < .001), hypertension (OR, 2.07; 95% CI, 1.09-3.92; P = .026), and current smoking (OR, 2.58; 95% CI, 1.28-5.23; P = .008). There were significantly more ADs (2.5 +/- 2.0 vs 1.8 +/- 1.6, P = .009) and ADs were of larger size (6.7 +/- 5.0 vs 5.3 +/- 3.6 mm, P = .027) in TSA patients than in AD-only patients. Furthermore, advanced adenoma and high-risk adenoma were more frequently observed in TSA patients than in AD-only patients (24.2% vs 11.2%, P = .002; 43.5% vs 23.6%, P < .001). Conclusions: The prevalence of TSA in healthy adults was .4%. Age >= 50 years, hypertension, and current smoking may be risk factors of TSA. Synchronous AD is often observed with TSA and may show more advanced features than those in AD-only patients.