Anatomical Distribution and Prevalence of Dysplasia in Sessile Serrated Lesions: A Cohort Study Over Seven Years.

BACKGROUND AND AIMS: Sessile serrated lesions (SSLs) progress to colorectal cancer via a critical intermediary stage, SSL with dysplasia (SSLd). Data on the anatomical distribution of SSLd are limited, particularly in high-detection-rate settings. This study aimed to assess the prevalence and anatomical distribution of dysplasia in SSLs from a single-endoscopist practice with a consistently high SSL detection rate over 7 years. METHODS: A retrospective analysis was conducted on all SSLs submitted to private pathology from a single endoscopist at Port Macquarie, Australia, between January 2019 and December 2025. Pathology reports were systematically reviewed, and terminology was standardized according to the 2019 World Health Organization Classification of Tumours of the Digestive System. Dysplasia was classified as a binary variable (present or absent) and attributed specifically to the SSL component. All specimens initially identified as SSLd were presented at the institutional histopathology meeting for review and reclassified where appropriate. RESULTS: A total of 3570 SSLs were identified across 2701 colonoscopy episodes. On initial pathology reporting, 102 SSLs were identified as harboring dysplasia (2.86%). After histopathology meeting review, 9 were reclassified (collision-type lesions of separate tubular adenoma and SSL in 3 cases, no dysplasia on review in 3 cases, traditional serrated adenoma in 2 cases, and conventional adenoma with a serrated growth pattern in 1 case), leaving 93 confirmed SSLd (2.61%). The confirmed dysplasia rate did not differ significantly between proximal (52/2114; 2.46%) and distal (25/824; 3.03%) colonic locations (P = .46). No individual anatomical site demonstrated a significantly different dysplasia rate. Colonoscopy episodes containing dysplastic SSLs had a higher mean number of synchronous SSLs compared to non-dysplastic episodes (1.6 vs 1.3; P = .005). CONCLUSION: In a large single-endoscopist pathology cohort, 2.61% of SSLs harbored confirmed cytological dysplasia after histopathology review. The reclassification rate of 8.8% was lower than the 33.3% reported in a prospective study with formal dual-expert pathologist review, though the pattern of reclassification was similar. Dysplasia was distributed throughout the colorectum without a significant proximal-distal predilection.