Introduction Colorectal cancer is now thought to arise from more than one molecular pathway. Lately, the serrated pathway has been placed in the limelight as it may account for 20–30% of colorectal cancers. However, sessile serrated lesions are easily missed on colonoscopy and in histopathological analysis despite their neoplastic potential. We conducted an observational study to understand the presentation, characteristics and significance of sessile serrated lesions detected in colonoscopies done for a variety of indications.

Methods A retrospective analysis of all sessile serrated lesions identified through the colorectal histopathological database from January 2012 – March 2015 was performed in our tertiary centre. Histology was reported by specialist gastrointestinal pathologists as per national standards.

Results 138 colonoscopies were performed in 118 patients who were found to have sessile serrated lesions. The table below shows the breadth of indications for colonoscopy in these cases. A total of 351 serrated lesions were noted, with just over half in the right colon (180/351, 51.3%). 67/351 polyps were >1 cm in size. 42/118 patients did have polyps noted on previous colonoscopies (19 had serrated lesions). The prevalence of co-existing adenomas in this cohort was 50% (59/118).

A subgroup analysis identified 13 patients in the entire cohort who met the WHO criteria for serrated polyposis syndrome. 4 of these patients (4/13; 30.8%) had been diagnosed with colorectal cancer in the past compared with 16/105 (15.2%) in the non serrated polyposis syndrome group. Only 8/13 patients underwent genetic screening and of this, 2 had hyperplastic polyposis syndrome and 2 had MYH polyposis.

Conclusion This large series of sessile serrated lesions has demonstrated the heterogeneity of circumstances in which they are detected during colonoscopy. Only 16% of patients were found to have serrated lesions on a previous colonoscopy. This may indicate that a large proportion of these polyps were missed or not recognised previously.

A small proportion of these patients will have a serrated polyposis syndrome that increases their colorectal cancer risk even further and genetic screening is advocated in all these patients.

Disclosure of Interest None Declared