Sessile Serrated Lesions, Unspecified Serrated Polyps, and Colorectal Cancer Risk

Sessile Serrated Lesions, Unspecified Serrated Polyps, and Colorectal Cancer Risk

Douglas K. Rex, MD, MASGE, reviewing Li D, et al. Gut 2021 Aug 11.

This study examined the risk of colorectal cancer (CRC) associated with serrated polyp subtypes in patients undergoing their first colonoscopy between 2006 and 2016. There were 695 persons who later developed CRC and 3475 controls. Two expert pathologists reviewed all serrated lesions to characterize them as sessile serrated lesions (SSLs), unspecified serrated polyps (USPs), hyperplastic polyps (HPs), or traditional serrated adenomas (TSAs). A USP is a lesion that has equivocal changes that do not allow for a diagnosis of SSL. 

The kappa statistics for SSL and HP diagnosis by the 2 pathologists were 0.9 and 0.74, respectively. 

Among all cases combined, the serrated polyp subtypes included 22% SSLs, 51% HPs, 27% USPs, and <1% TSAs. There were no unequivocal large proximal HPs.

The table below shows the adjusted odds ratios (aORs) for CRC at follow-up.

  aOR (compared to no polyp)

SSL without dysplasia          3.3

SSL with dysplasia        10.3

Proximal large SSL        12.8

SSL plus adenoma          4.4

HP alone                  0.8

USP alone                  1.8

USP plus adenoma                  2.6

Conventional adenoma          2.2

Advanced adenoma                  3.1

In both SSLs and USPs, the risk was almost entirely associated with proximal lesions, not distal lesions. 

The CRC risk with SSLs alone was more than twice as high in women as in men.

Douglas K. Rex, MD, FASGE


In clinical practice, many pathologists are not using the classification “unspecified SP.” With time, there seems to have been an increasing tendency of pathologists to call serrated lesions “SSLs” rather than “HPs.” In this study, the increased risk of CRC associated with both SSLs and unspecified SPs suggests that the apparent ever-increasing bias toward the use of the category “SSL” is almost certainly the best thing for patients. In clinical practice, lesions that are ≥10 mm in size and called hyperplastic are treated as SSLs. This study with expert pathologists suggests that’s the right approach because there is no such thing as an unequivocal HP ≥10 mm. Overall, these data suggest that the subsequent risk of CRC after SSL diagnosis is as great as that after adenoma diagnosis. Given that the risk of cancer in SSLs compared with adenomas of equal size is much lower, these data suggest that SSLs may be a marker for missed lesions. The combination of SSLs and a poor detector may be particularly deadly.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Li D, Doherty AR, Raju M, et al. Risk stratification for colorectal cancer in individuals with subtypes of serrated polyps. Gut 2021 Aug 11. (Epub ahead of print) (

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