Endoscopic diagnosis of colorectal serrated lesions: Current status and future perspectives based on the results of a questionnaire survey

Immunohistochemical Examination is Highly Sensitive and Specific for Detection of the V600E BRAF Mutation in Colorectal Serrated Lesions

Mutations in BRAF are important events in colorectal serrated lesions and specific genetic markers for the serrated pathway. However, examination of BRAF mutations is not easy in routine histopathologic analyses. Here, the authors examined 73 colorectal serrated lesions, including 21 hyperplastic polyps, 32 traditional serrated adenomas, and 30 sessile serrated lesions, for comparison of BRAF mutation status with immunopositive expression of the anti-BRAF V600E mutation-specific antibody VE1. Thirty-two tubular adenomas (TAs) were examined as controls. In addition, 5 examples of sessile serrated lesion with dysplasia were included. Mutations in BRAF (exon 15; V600E) and KRAS (exon 2) were analyzed in serrated lesions and TAs using pyrosequencing. Finally, the authors compared BRAF mutations with immunohistochemical expression of VE1 antibodies against the BRAF V600E mutation, which was examined based on quantitative analyses and correlations between semiquantitative (0, 1+, or 2+) and quantitative results in colorectal serrated lesions. The cut-off value of VE1 expression (32%) was set based on receiver operating characteristic curve analysis. In the current study, mutations in BRAF were well correlated with VE1 expression in serrated lesions, although no TAs without BRAF mutations were immunopositive. In contrast, serrated lesions and TAs with mutations in KRAS were not stained for VE1 expression. In serrated lesions, although the sensitivity was 96.2% to 100%, the specificity was 90.0% to 100%. In addition, there was also good correlation between semiquantitative and quantitative results. Analysis of BRAF V600E expression may be pathologically useful, particularly in routine histopathologic diagnosis.

Prevalence of serrated lesions, risk factors, and their association with synchronous advanced colorectal neoplasia in asymptomatic screened individuals

BACKGROUND AND AIM

Serrated lesions (SLs) have attracted attention as precursors of colorectal cancer (CRC). However, their prevalence, risk factors, and clinical significance have not been satisfactorily elucidated. This study used high-quality colonoscopy data to determine the prevalence of SLs and to identify their risk factors and relationship with synchronous advanced colorectal neoplasia (ACN) in asymptomatic screened individuals.

METHODS

This study included data for 5218 individuals who underwent first-time screening colonoscopy by highly experienced endoscopists. The relationships between baseline characteristics and the presence of SLs and those between the presence of SLs and synchronous ACN were assessed using the chi-squared test and multivariate logistic regression.

RESULTS

The proportions of individuals with SLs and right-sided SLs were 23.3% and 7.6%, respectively. Age, sex, family history of CRC, smoking, and body mass index were significantly related with the presence of SLs, and current smoking was most strongly associated with SLs (adjusted odds ratio [aOR] 2.6, 95% confidence interval [CI] 2.1-3.2). The aOR (95% CI) of the presence of SLs, SLs sized ≥ 10 mm, and right-sided SLs ≥ 5 mm for synchronous ACN was 1.4 (1.1-1.9), 3.5 (1.3-9.6), and 1.9 (1.0-3.8), respectively. The presence of left-sided SLs ≥ 10 mm (without right-sided SLs) was also significantly associated with ACN (aOR 8.1, 95% CI 2.0-33.7).

CONCLUSIONS

The relatively high prevalence of SLs and risk factors in screened individuals were elucidated and the significant relationship between SLs, particularly SLs ≥ 10 mm and right-sided SLs ≥ 5 mm, and synchronous ACN was confirmed.

Narrow-Band Imaging: Clinical Application in Gastrointestinal Endoscopy

Narrow-band imaging is an advanced imaging system that applies optic digital methods to enhance endoscopic images and improves visualization of the mucosal surface architecture and microvascular pattern. Narrow-band imaging use has been suggested to be an important adjunctive tool to white-light endoscopy to improve the detection of lesions in the digestive tract. Importantly, it also allows the distinction between benign and malignant lesions, targeting biopsies, prediction of the risk of invasive cancer, delimitation of resection margins, and identification of residual neoplasia in a scar. Thus, in expert hands it is a useful tool that enables the physician to decide on the best treatment (endoscopic or surgical) and management. Current evidence suggests that it should be used routinely for patients at increased risk for digestive neoplastic lesions and could become the standard of care in the near future, at least in referral centers. However, adequate training programs to promote the implementation of narrow-band imaging in daily clinical practice are needed. In this review, we summarize the current scientific evidence on the clinical usefulness of narrow-band imaging in the diagnosis and characterization of digestive tract lesions/cancers and describe the available classification systems.

Sessile Serrated Polyps and Colon Cancer Prevention

Evidence suggests that up to one fifth of colorectal carcinomas develop from serrated polyps, named for their pattern of colonic crypts, and include the sessile serrated adenoma/polyp (SSA/P) that has malignant potential. SSA/Ps are typically located in the proximal colon and have molecular features of hypermethylation of CpG islands in gene promoters and activating point mutations (V600E) in the BRAF oncogene. Both of these features are seen in sporadic colorectal carcinomas with microsatellite instability (MSI) which is potentially consistent with an origin of these cancers from precursor SSA/Ps. Dysplasia is detected in a subset of SSA/Ps with a high risk of progression to carcinoma. An uncommon serrated polyp is the traditional serrated adenoma that is typically found in the left colon, has a tubulovillous architecture, and frequently harbors mutant KRAS To date, the epidemiology of these serrated lesions is poorly understood, and limited observational data suggest a potential chemopreventive benefit of nonsteroidal anti-inflammatory drugs. The current primary strategy to reduce the risk of colorectal carcinoma from serrated polyps is to enhance their detection at colonoscopy and to ensure their complete removal. This review provides insight into the epidemiologic, clinical, histopathologic, and molecular features of serrated polyps and includes data on their endoscopic detection and chemoprevention. Cancer Prev Res; 10(5); 270-8. ©2017 AACR.