Sessile serrated adenoma is a relatively recently described entity that can occur in the appendix. The incidence of this finding is unknown. We entirely submitted 100 consecutive appendices sent for acute appendicitis and correlated the histologic findings with clinical parameters and the findings in 100 routinely (partially) submitted cases. In cases submitted routinely, only 1 sessile serrated adenoma was found. In contrast, in cases entirely submitted, 11 adenomas were found, all in patients 30 years or older. All sessile serrated adenomas were present in 3 cross-sections or fewer of the appendix. The incidence of sessile serrated adenoma in patients with acute appendicitis is significantly increased in patients 30 years or older (P = .001), and detection is dependent on thorough tissue sampling.