The article contains a literature review of clinical cases describing sessile serrated adenomas in the appendix from 1998 to 2018. Currently, it is still diffi cult to assess the true incidence of this pathology due to the fact that in most cases serrated adenomas are accidental fi ndings diagnosed after removing an inflamed appendix, since often, at small sizes, they do not cause clinical symptoms, do not bother patients and are inaccessible for endoscopic examination (if located behind its orifi ce). In addition, we present 2 clinical cases of sessile serrated adenoma of the appendix in patients who were admitted to the City Clinical Hospital No. 31 of the Moscow City Health Department in 2018 due to acute appendicitis, with a clinical and morphological characteristic, including a molecular genetics study.