A sessile serrated polyp is a serrated polyp that demonstrates abnormal cellular proliferation characterized by a proximally displaced proliferative zone, epithelial serrations, and characteristic distorted basilar crypt architecture with crypt dilation, branching, and lateral growth along the muscularis mucosa. The disease is Experimental Factor Ontology entry EFO_0008523 (sessile serrated polyp). Also known as: serrated adenoma type I, serrated polyp with abnormal proliferation, sessile serrated adenoma/polyp, sessile serrated polyp/adenoma.