Histology subtypes and polyp size are associated with synchronous colorectal carcinoma of colorectal serrated polyps: a study of 499 serrated polyps

Abstract

Sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA) are considered as precursors of colorectal cancer, and are often diagnostic challenges. Their true prevalence is masked by significant inter-observer variations. To investigate the true prevalence and synchronous colorectal carcinoma (sCRC) of colorectal serrated polyps (CSP) and their associated factors, we first retrospectively identified all colorectal polyps collected at our institution between June 1995 and May 2013. After centrally reclassifying all CSP to reduce inter-observer variations, Chi-square tests and logistic regression analyses were used to analyze the potential factors. Among the included 5501 colorectal polyps, 499 CSP of 428 patients were identified and studied, including 353 hyperplastic polyps (HP, 70.7%), 80 SSA (16.0%), 61 TSA (12.2%) and 5 mixed polyp (1.0%). Diagnostic disagreements were found in 68 CSP (13.63% of CSP). SSA and TSA were more often larger than 5 mm and in proximal colon than HP. SSA were also more likely associated with older age (p=0.005), size ≥5 mm (p<0.001) and ≥3 polyps (p=0.004) than HP in distal colon, but only more likely associated with older age (p=0.006) in proximal colon. Multivariate regression analysis demonstrated that CSP with sCRC, compared with CSP without sCRC, were linked to CSP size ≥1 cm (vs <1 cm, odds ratio [OR] 4.412, 95% confidence interval [CI] 1.684-11.556, P=0.003) and a diagnosis of SSA or TSA (vs HP, OR 6.194, 95% CI 1.870-20.513, P=0.003 and OR 6.754, 95% CI 1.981-23.028, P=0.002, respectively), but not age, gender, polyp number and polyp shape. SSA and TSA are similarly often associated with sCRC (P=0.460). In conclusion, histology subtypes and polyp size may serve as markers for sCRC of CSP. SSA and TSA may warrant careful endoscopic examinations and similar follow-up intervals.

Keywords: Conventional adenoma; colon; hyperplastic polyp; sessile serrated adenoma; traditional serrated adenoma.

Figure 1

Representative photomicrographs of CSP: A. HP (×40); B. SSA (×40); C. TA and HP (mixed polyp) (×40); D. TSA (×40); E. Polyp with indeterminate features between SSA and HP (×40); F. An sCRC (bold arrow) and residual SSA with cytological dysplasia (thin arrow) (×40). CSP, colorectal serrated polyp; HP, hyperplastic polyp; SSA, sessile serrated adenoma; TSA, traditional serrated adenoma; TA, tubular adenoma; sCRC, synchronous colorectal cancer.

Figure 2

The discordant diagnoses between the two groups of pathologists. HP, hyperplastic polyp; SSA, sessile serrated adenoma; TSA, traditional serrated adenoma; TA, tubular adenoma; MP, mixed polyp; IP, inflammatory polyp.

Figure 3

Prevalence of different colorectal polyps in our study. HP, hyperplastic polyp; SSA, sessile serrated adenoma; TSA, traditional serrated adenoma; TA, tubular adenoma; MP, mixed polyp; IP, inflammatory polyp; OP, other types of polyps including polypoid hyperplasia, adenomatoid hyperplasia, juvenile polyp, hamartomatous polyp and mixed polyp.