Sporadic colorectal cancers with a high degree of microsatellite instability are a clinically distinct subgroup with a high incidence of BRAF mutation.
These cancers are widely considered to develop from serrated polyps.
Previous studies of serrated polyps have been highly selected and largely retrospective.
Dr Kevin Spring and colleagues from Australia examined the prevalence of sessile serrated adenomas.
The investigative team then determined the incidence of BRAF and K-ras mutations in different types of polyps.
The team evaluated an unselected consecutive series of 190 patients underwent magnifying chromoendoscopy.
|Sessile serrated adenomas were found in 9% of patients|
Polyp location, size, and histologic classification were recorded.
All polyps were screened for BRAF V600E and K-ras codon 12 and 13 mutations.
The investigators detected polyps in 72% of patients.
The team noted that 60% were adenomas, and followed by hyperplastic polyps in 29%.
The team found sessile serrated adenomas in 9%, traditional serrated adenomas in less than 1%, and mixed polyps in 2%.
Adenomas were more prevalent in the proximal colon in 73%, as were sessile serrated adenomas found in 75% of patients.
The team observed that the adenomas were large.
The presence of at least one sessile serrated adenoma was associated with increased polyp burden, and female sex.
BRAF mutation was rare in adenomas but common in sessile serrated adenomas, traditional serrated adenomas.
The investigators found that BRAF mutation was also common in mixed polyps, and microvesicular hyperplastic polyps.
K-ras mutations were significantly associated with goblet cell hyperplastic polyps and tubulovillous adenomas.
Dr Spring's team concludes, “The prevalence of sessile serrated adenomas is approximately 9% in patients undergoing colonoscopy.”
“They are associated with BRAF mutation, proximal location, female sex, and presence of multiple polyps.”
“These findings emphasize the importance of identifying and removing these lesions for endoscopic prevention of colorectal cancer.”