Clinical and endoscopic characteristics of colorectal traditional serrated adenomas with dysplasia/adenocarcinoma in a Korean population

BACKGROUND Traditional serrated adenoma(TSA)is a rare and precancerous lesion of colorectal cancer.The clinical and endoscopic differentiations between TSAs without dysplasia or adenocarcinoma(TSAOs)and TSAs with dysplasia or adenocarcinoma(TSADs)remain unclear.AIM To evaluate the characteristics of colorectal TSAs and compare the characteristics of TSAOs with those of TSADs.METHODS This retrospective study included 193 patients who underwent endoscopic resection and received a pathologic diagnosis of TSA.We reviewed the medical,endoscopic,and histopathologic records of patients who underwent endoscopic resection of TSAs between January 2010 and December 2023.RESULTS TSAs were more frequently located in the rectosigmoid colon.Most TSAs had 0-Ip,0-Isp,or 0-Is morphologies.The TSAD lesions were larger than TSAO lesions.TSAD lesions more commonly had a red color and an irregular border than TSAO lesions.TSAOs were usually treated using conventional endoscopic mucosal resection,whereas TSADs were treated using conventional endoscopic mucosal resection,endoscopic submucosal dissection,and surgery.Post-polypectomy bleeding was more common with TSADs than with TSAOs.Univariate analysis showed that gastrointestinal bleeding,red color,0-IIa,irregular border,and lobular mucosal surface were significantly associated with TSADs.Multivariate analysis showed that gastrointestinal bleeding,an irregular border,and a lobular mucosal surface were significantly associated with TSADs.CONCLUSION TSAs with gastrointestinal bleeding,an irregular border,and a lobular mucosal surface are associated with an increased risk of dysplasia or adenocarcinoma.

Superficial Serrated Adenoma (SuSA): A New Subtype of Serrated Lesions

Superficial serrated adenoma (SuSA) is a new subtype of serrated lesions proposed in recent years, most of which are located in the sigmoid colon or rectum, with typical mixed adenoma and serrated pathological features, and its molecular features are high frequency of KRAS mutation and RSPO fusion or overexpression. At present, it is believed that SuSA has two subtypes: traditional serrated adenoma (TSA)-associated SuSA and isolated SuSA. Solitary SuSA showed faded pedicle-free protuberant lesions under endoscope and lobulated, pp (pit pattern) classification was type II and type IIIH, TSA-associated SuSA showed double-layer eminence, SuSA part showed white flat eminence, pp classification showed type II and IIIH, TSA part showed red tone high eminence, pp was IVH type. SuSA can develop into colorectal cancer through the evolution of TSA, and it can also directly develop into MSS colorectal cancer. In view of the superficial understanding of SuSA and the lack of a complete description of SuSA, this paper review the research progress of SuSA at home and abroad from the origin, endoscope features, histopathological features, molecular biology, differential diagnosis and treatment of SuSA, in order to better promote the understanding and clinical diagnosis of lesions.

Sessile serrated adenomas:Demographic,endoscopic and pathological characteristics

AIM:To study the demographic and endoscopic characteristics of patients with sessile serrated adenoma(SSA) in a single center.METHODS:Patients with SSA were identified by review of the pathology database of Mayo Clinic Arizona from 2005 to 2007.A retrospective chart review was performed to extract data on demographics,polyp characteristics,presence of synchronous adenomatous polyps or cancer,polypectomy methods,and related complications.RESULTS:One hundred and seventy-one(2.9%) of all patients undergoing colonoscopy had a total of 226 SSAs.The mean(SE) size of the SSAs was 8.1(0.4) mm;42% of SSAs were ≤ 5 mm,and 69% were ≤ 9 mm.Fifty-one per cent of SSAs were located in the cecum or ascending colon.Approximately half of the patients had synchronous polyps of other histological types,including hyperplastic and adenomatous polyps.Synchronous adenocarcinoma was present in seven(4%) cases.Ninety-seven percent of polyps were removed by colonoscopy.CONCLUSION:Among patients with colon polyps,2.9% were found to have SSAs.Most of the SSAs were located in the right side and were safely managed by colonoscopy.

Case of pediatric traditional serrated adenoma resected via endoscopic submucosal dissection

Traditional serrated adenoma(TSA)is a type of serrated polyp of the colorectum and is thought to be a precancerous lesion.There are three types of serrated polyps,namely,hyperplastic polyps,sessile serrated adenomas/polyps,and TSAs.TSA is the least common of the three types and accounts for about 5% of serrated polyps.Here we report a pediatric case of TSA that was successfully resected by endoscopic submucosal dissection(ESD).This rare case report describes a pediatric patient with no family history of colonic polyp who was admitted to our hospital with hematochezia.On colonoscopy,we found a polypoid lesion measuring 10 mm in diameter in the lower rectum.We selected ESD as a surgical option for en bloc resection,and histopathological examination revealed TSA.The findings in this case suggest that TSA with precancerous potential can occur in children,and that ESD is useful for treating this lesion.

Correlations of morphology and molecular alterations in traditional serrated adenoma

Traditional serrated adenoma was first reported by Longacre and FenoglioPresier in 1990.Their initial study described main features of this lesion,but the consensus diagnostic criteria were not widely adopted until recently.Traditional serrated adenoma presents with grossly protuberant configuration and pineconelike appearance upon endoscopy.Histologically,it is characterized by ectopic crypt formation,slit-like serration,eosinophilic cytoplasm and pencillate nuclei.Although much is now known about the morphology and molecular changes,the mechanisms underlying the morphological alterations are still not fully understood.Furthermore,the origin of traditional serrated adenoma is not completely known.We review recent studies of the traditional serrated adenoma and provide an overview on current understanding of this rare entity.

From traditional serrated adenoma to tubulovillous adenoma and beyond

It is well established that colorectal cancer develops from a series of precursor epithelial polyps, including tubular adenomas, villous/tubulovillous adenomas (VA/TVA), sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA). Of these, TSAs are least common and account for only 5% of all serrated polyps. TSAs are characterised by the presence of a “pinecone-like” architecture, granular eosinophilic cytoplasm, luminal serrations, ectopic crypt foci (ECF) and elongated, pencillate nuclei. However, the distinct slit-like luminal serrations, reminiscent of small bowel mucosa, appear to be the most unique and reproducible feature to distinguish TSAs from other polyps. There is a contention that TSAs are not inherently dysplastic and that the majority do not show cytological atypia. Two types of dysplasia are associated with TSA. Serrated dysplasia is less well recognised and less commonly encountered than adenomatous dysplasia. In addition, it is now becoming increasingly evident that TSAs can be admixed with HP, SSA and VA/TVA. At a genetic level, polyps may switch phenotype as they accumulate genetic changes, evolving from a serrated pathway to a more conventional one, which could be the basis for a spectrum theory starting out with a TSA with serration and ECF evolving into a TSA with conventional dysplasia and, eventually, to a well-developed conventional adenoma. Nevertheless, there is an exigency for future studies to provide further illumination and bridge the gaps in our present understanding.

Improving sessile serrated adenoma detection rates with high definition colonoscopy:A retrospective study

BACKGROUND Sessile serrated adenomas(SSAs)are important premalignant lesions that are difficult to detect during colonoscopy due to poor definition,concealment by mucous caps,and flat appearance.High definition(HD)colonoscopy may uniquely aid in the detection of these inconspicuous lesions compared to standard definition(SD)colonoscopes.In the absence of existing clinical guidelines to obligate the use of HD colonoscopy for colorectal cancer screening in average-risk patients,demonstrating the benefit of HD colonoscopy on SSA detection rate(SSADR)may help strengthen the evidence to recommend its use in all settings.AIM To evaluate the benefit of HD colonoscopy compared to SD colonoscopy on SSADR in average-risk patients undergoing screening colonoscopy.METHODS Data from screening colonoscopies for patients aged 50-76 years two years before and two years after the transition from SD colonoscopy to HD colonoscopy at our large,academic teaching center were collected.Patients with symptoms of colorectal disease,positive occult blood test,history of colon polyps,cancer,polyposis syndrome,inflammatory bowel disease or family history of colon cancer or polyps were excluded.Patients whose endoscopists did not perform colonoscopies both before and after scope definition change were also excluded.Differences in individual endoscopist SSADR,average SSADR,and overall SSADR with SD colonoscopy vs HD colonoscopy were also evaluated for significance.RESULTS A total of 3657 colonoscopies met eligibility criteria with 2012 colonoscopies from the SD colonoscopy period and 1645 colonoscopies from the HD colonoscopy period from a pool of 11 endoscopists.Statistically significant improvements of 2.30%in mean SSADR and 2.53%in overall SSADR were noted with HD colonoscopy(P=0.00028 and P=0.00849,respectively).On the individual level,three endoscopists experienced statistically significant benefit with HD colonoscopy(+5.74%,P=0.0056;+4.50%,P=0.0278;+4.84%,P=0.03486).CONCLUSION Our study suggests that HD colonoscopy statistically significantly improves sessile serrated adenoma detection rate in the screening of average risk patients during screening colonoscopy.By improving the detection and removal of these lesions,adoption of HD colonoscopy may reduce the significant premalignant burden of sessile serrated adenomas.

Solitary rectal ulcer syndrome complicating sessile serrated adenoma/polyps: A case report and review of literature

Solitary rectal ulcer syndrome(SRUS) is a rare benign condition, which can mimic many other diseases because of their similarities in clinical, endoscopic and histological features. Sessile serrated adenoma/polyp(SSA/p) is a premalignant lesion in the colon and rectum. The misdiagnosis of SSA/p in SRUS patients has been noted, but the case of SRUS arising secondarily to SSA/p has been rarely reported. We herein report the case of a 59-year-old man who presented with an ulcerative nodular lesion in the rectum, accompanied by the symptoms of blood and mucus in the feces, diarrhea and constipation. Magnetic resonance imagining revealed thickening of the rectal mucosa-submucosa. Histologically, the lesion was characterized by the hyperplastic lamina propria and diffusely serrated crypts. Further immunohistochemical staining showed the loss of HES1 and MLH1 expression in the epithelial cells in the serrated area. The patient with SRUS had histological changes of SSA/p, suggesting a potential of tumor transformation in certain cases. SRUS uncommonly accompanied by serrated lesions should at least be considered by pathologists and clinicians.

Clinicopathological features and expression of regulatory mechanism of the Wnt signaling pathway in colorectal sessile serrated adenomas/polyps with different syndrome types

BACKGROUND Colorectal cancer(CRC)is the third most common cancer worldwide,with the fourth highest mortality among all cancers.Reportedly,in addition to adenomas,serrated polyps,which account for 15%-30%of CRCs,can also develop into CRCs through the serrated pathway.Sessile serrated adenomas/polyps(SSAs/Ps),a type of serrated polyps,are easily misdiagnosed during endoscopy.AIM To observe the difference in the Wnt signaling pathway expression in SSAs/Ps patients with different syndrome types.METHODS From January 2021 to December 2021,patients with SSAs/Ps were recruited from the Endoscopy Room of Shanghai Traditional Chinese Medicine-Integrated Hospital,affiliated with Shanghai University of Traditional Chinese Medicine.Thirty cases each of large intestine damp-heat(Da-Chang-Shi-Re,DCSR)syndrome and spleen-stomach weakness(Pi-Wei-Xu-Ruo)syndrome were reported.Baseline comparison of the general data,typical tongue coating,colonoscopy findings,and hematoxylin and eosin findings was performed in each group.The expression of the Wnt pathway-related proteins,namelyβ-catenin,adenomatous polyposis coli,and mutated in colorectal cancer,were analyzed using immunohistochemistry.RESULTS Significant differences were observed with respect to the SSAs/Ps size between the two groups of patients with different syndrome types(P=0.001).The other aspects did not differ between the two groups.The Wnt signaling pathway was activated in patients with SSAs/Ps belonging to both groups,which was manifested asβ-catenin protein translocation into the nucleus.However,SSAs/Ps patients with DCSR syndrome had more nucleation,higherβ-catenin expression,and negative regulatory factor(adenomatous polyposis coli and mutated in colorectal cancer)expression(P<0.0001)than SSA/P patients with Pi-Wei-Xu-Ruo syndrome.In addition,the SSA/P size was linearly correlated with the related protein expression.CONCLUSION Patients with DCSR syndrome had a more obvious Wnt signaling pathway activation and a higher risk of carcinogenesis.A high-quality colonoscopic diagnosis was essential.The thorough assessment of clinical diseases can be improved by combining the diseases of Western medicine with the syndromes of traditional Chinese medicine.

Clinico-pathological aspects of colorectal serrated adenomas

AIM： To study the association of colorectal serrated adenomas （SAs） with invasive carcinoma, local recurrence, synchronicity and metachronicity of lesions. METHODS： A total of 4536 polyps from 1096 patients over an eight-year period （1987-1995） were retrospectively examined. Adenomas showing at least 50% of serrated architecture were called SAs by three reviewing pathologists. RESULTS： Ninety-one （2%） of all polyps were called SAs, which were found in 46 patients. Invasive carcinomas were seen in 3 out of 46 （6.4%） patients, of whom one was a case of familial adenomatous polyposis （FAP）. A male preponderance was noted and features of a mild degree of dysplasia were seen in majority （n=75, 83%） of serrated adenomas. Follow-up ranged 1-12 years with a mean time of 5.75 years. Recurrences of SAs were seen in 3 （6.4%） cases, synchronous SAs in 16 （34.8%） cases and metachronous SAs in 9 （19.6%） cases. CONCLUSION： Invasive carcinoma arising in serrated adenoma is rare, accounting for 2 （4.3%） cases studied in this series.

Significance of EZH2 and BMI-1 Protein Expression in Carcinogenesis of Colon Serrated Adenoma

Objective:To observe the significance of EZH2 and BMI-1 protein expression in the carcinogenesis process of colon serrated adenoma(SSA/P).Methods:Hematoxylin-eosin(HE)staining was used to observe the morphological characteristics of normal tissues,hyperplastic polyp(HP),SSA/P and colon cancer.Immunohistochemical staining was used to detect the expression of EZH2 and BMI-1 protein.The relative expression of EZH2 and BMI-1 was detected by qRT-PCR.Results:Compared with normal tissues,HP and colon cancer tissues,SSA/P showed serrated glandular hyperplasia,glandular dilatation,and deep nuclear staining,which had certain atypia.The positive expression rates of EZH2 and BMI-1 protein were 53.3%and 56%,which were close to those of colon cancer(66.7% and 76.6%)and higher than those of normal group and HP(16% and 8%,P<0.05).The relative expression of EZH2 and BMI-1 in SSA/P tissue was significantly higher than that in normal group and HP,but lower than that in carcinogenesis group(P<0.05).Conclusion:EZH2 and BMI-1 play an important role in the carcinogenesis of colon serrated adenoma,and can be used as the primary screening index before carcinogenesis.

How to"pick up"colorectal serrated lesions and polyps in daily histopathology practice:From terminologies to diagnostic pitfalls

Over the last decade,our knowledge of colorectal serrated polyps and lesions has significantly improved due to numerous studies on this group of precursor lesions.Serrated lesions were misleading as benign before 2010,but they are currently reclassified as precancerous lesions that contribute to 30%of colorectal cancer through the serrated neoplasia pathway.The World Health Organization updated the classification for serrated lesions and polyps of the colon and rectum in 2019,which is more concise and applicable in daily practice.The responsible authors prescribe that“colorectal serrated lesions and polyps are characterized by a serrated(sawtooth or stellate)architecture of the epithelium.”From a clinical standpoint,sessile serrated lesion(SSL)and SSL with dysplasia(SSLD)are the two most significant entities.Despite these advancements,the precise diagnosis of SSL and SSLD based mainly on histopathology remains challenging due to various difficulties.This review describes the nomenclature and the terminology of colorectal serrated polyps and lesions and highlights the diagnostic criteria and obstacles encountered in the histopathological diagnosis of SSL and SSLD.

Serrated polyps of the colon and rectum:Remove or not?

In recent years,the serrated neoplasia pathway where serrated polyps arise as a colorectal cancer has gained considerable attention as a new carcinogenic pathway.Colorectal serrated polyps are histopathologically classified into hyperplastic polyps(HPs),sessile serrated lesions,and traditional serrated adenomas;in the serrated neoplasia pathway,the latter two are considered to be premalignant.In western countries,all colorectal polyps,including serrated polyps,apart from diminutive rectosigmoid HPs are removed.However,in Asian countries,the treatment strategy for colorectal serrated polyps has remained unestablished.Therefore,in this review,we described the clinicopathological features of colorectal serrated polyps and proposed to remove HPs and sessile serrated lesions≥6 mm in size,and traditional serrated adenomas of any size.

Serrated neoplasia of the colorectum

Serrated polyps of the colorectum form a group of related lesions which include aberrant crypt foci (ACF), conventional hyperplastic polyps, mixed (admixed) polyps, serrated adenomas and sessile serrated adenomas. In recent years the molecular differences between these morphologically similar lesions have been highlighted, and their differing biological potential has been realised. In particular, the sessile serrated adenoma has become recognised as the precursor lesion to a group of sporadic colorectal carcinomas characterised by morphological and molecular features distinct from conventional adenomas. These recent findings have challenged the long held paradigm that all colorectal carcinomas arise via the traditional adenoma-carcinoma sequence. In addition, they present a major challenge for the early detection and management of colorectal cancer, which is no longer regarded as a homogeneous entity.

Serrated lesions:A challenging enemy

The serrated pathway accounts for 30%-35%of colorectal cancer(CRC).Unlike hyperplastic polyps,both sessile serrated lesions(SSLs)and traditional serrated adenomas are premalignant lesions,yet SSLs are considered to be the principal serrated precursor of CRCs.Serrated lesions represent a challenge in detection,classification,and removal–contributing to post-colonoscopy cancer.Therefore,it is of the utmost importance to characterize these lesions properly to ensure complete removal.A retrospective cohort study developed a diagnostic scoring system for SSLs to facilitate their detection endoscopically and subsequent removal.From the study,it can be ascertained that both indistinct border and mucus cap are essential in both recognizing and diagnosing serrated lesions.The proximal colon poses technical challenges for some endoscopists,which is why high-quality colonoscopy plays such an important role.The indistinct border of some SSLs poses another challenge due to difficult complete resection.Overall,it is imperative that gastroenterologists use the key features of mucus cap,indistinct borders,and size of at least five millimeters along with a high-quality colonoscopy and a good bowel preparation to improve the SSL detection rate.

Evaluation of magnifying colonoscopy in the diagnosis of serrated polyps

AIM:To elucidate the colonoscopic features of serrated lesions of the colorectum using magnifying colonoscopy.METHODS:Broad division of serrated lesions of the colorectum into hyperplastic polyps(HPs),traditional serrated adenomas(TSAs),and sessile serrated adenomas/polyps(SSA/Ps) has been proposed on the basis of recent molecular biological studies.However,few reports have examined the colonoscopic features of these divisions,including magnified colonoscopic findings.This study examined 118 lesions excised in our hospital as suspected serrated lesions after magnified observation between January 2008 and September 2011.Patient characteristics(sex,age),conventional colonoscopic findings(location,size,morphology,color,mucin) and magnified colonoscopic findings(pit pattern diagnosis) were interpreted by five colonoscopists with experience in over 1000 colonoscopies,and were compared with histopathological diagnoses.The pit patterns were categorized according to Kudo's classification,but a more detailed investigation was also performed using the subclassification [type Ⅱ-Open(type Ⅱ-O),type Ⅱ-Long(type Ⅱ-L),or type Ⅳ-Serrated(type Ⅳ-S)] proposed by Kimura T and Yamano H.RESULTS:Lesions comprised 23 HPs(23/118:19.5%),39 TSAs(39/118:33.1%:with cancer in one case),50 SSA/Ps(50/118:42.4%:complicated with cancer in three cases),and six others(6/118:5.1%).We excluded six others,including three regular adenomas,one hamartoma,one inflammatory polyp,and one juvenile polyp for further analysis.Conventional colonoscopy showed that SSA/Ps were characterized as larger in diameter than TSAs and HPs(SSA/P vs HP,13.62 ± 8.62 mm vs 7.74 ± 3.24 mm,P < 0.001;SSA/Ps vs TSA,13.62 ± 8.62 mm vs 9.89 ± 5.73 mm,P < 0.01);common in the right side of the colon [HPs,30.4%(7/23):TSAs,20.5%(8/39):SSA/P,84.0%(42/50),P < 0.001];flat-elevated lesion [HPs,30.4%(7/23):TSAs,5.1%(2/39):SSA/Ps,90.0%(45/50),P < 0.001];normal-colored or pale imucosa [HPs,34.8%(8/23):TSAs,10.3%(4/39):SSA/Ps,80%(40/50),P < 0.001];and with large amounts of mucin [HPs,21.7%(5/23):TSAs,17.9%(7/39):SSA/Ps,72.0%(36/50),P < 0.001].In magnified colonoscopic findings,17 lesions showed either type Ⅱ pit pattern alone or partial type Ⅱ pit pattern as the basic architecture,with 14 HPs(14/17,70.0%) and 3 SSA/Ps.Magnified colonoscopy showed the type Ⅱ-O pit pattern as characteristic of SSA/Ps [sensitivity 83.7%(41/49),specificity 85.7%(54/63)].Cancer was also present in three lesions,in all of which a type Ⅵ pit pattern was also present within the same lesion.There were four HPs and four TSAs each.The type Ⅳ-S pit pattern was characteristic of TSAs [sensitivity 96.7%(30/31),specificity 89.9%(72/81)].Cancer was present in one lesion,in which a type Ⅵ pit pattern was also present within the same lesion.In our study,serrated lesions of the colorectum also possessed the features described in previous reports of conventional colonoscopic findings.The pit pattern diagnosis using magnifying colonoscopy,particularly magnified colonoscopic findings using subclassifications of surface architecture,reflected the pathological characteristics of SSA/Ps and TSAs,and will be useful for colonoscopic diagnosis.CONCLUSION:We suggest that this system could be a good diagnostic tool for SSA/Ps using magnifying colonoscopy.

Reinterpretation of histology of proximal colon polyps called hyperplastic in 2001

AIM： To evaluate how proximal colon polyps interpreted as hyperplastic polyps in 2001 would be interpreted by expert pathologists in 2007.METHODS： ≥ 5 mm in interpreted pathologists 2007 by 3 GI Forty consecutive proximal colon polyps size, removed in 2001, and originally as hyperplastic polyps by general at Indiana University, were reviewed in pathologists.CONCLUSION： Many polyps interpreted as hyperplastic in 2001 were considered sessile serrated lesions by GI pathologists in 2007, but there is substantial inter-observer variation amongst GI pathologists.

Hyperplastic polyposis associated with two asynchronous colon cancers

We report a patient with hyperplastic polyposis who had two asynchronous colon cancers, a combined adenoma-hyperplastic polyp, a serrated adenoma, and tubular adenomas. Hyperplastic polyposis is thought to be a precancerous lesion; and adenocarcinoma arises from hyperplastic polyposis through the hyperplastic polyp-adenoma-carcinoma sequence. Most polyps in patients with hyperplastic polyposis present as bland- looking hyperplastic polyps, which are regarded as non- neoplastic lesions; however, the risk of malignancy should not be underestimated. In patients with multiple hyperplastic polyps, hyperplastic polyposis should be identified and followed up carefully in order to detect malignant transformation in the early stage.

Detection Rate, Distribution, Clinical and Pathological Features of Colorectal Serrated Polyps

Background：Colorectal serrated polyp is considered as histologically heterogeneous lesions with malignant potential in western countries.However,few Asian studies have investigated the comprehensive clinical features of serrated polyps in symptomatic populations.The aim of the study was to evaluate the features of colorectal serrated polyps in a Chinese symptomatic population.Methods：Data from all consecutive symptomatic patients were documented from a large colonoscopy database and were analyzed.Chi-square test or Fisher＇s exact test and logistic regression analysis were used for the data processing.Results：A total of 9191 （31.7%） patients were detected with at least one colorectal polyp.The prevalence of serrated polyps was 0.53% （153/28,981）.The proportions of hyperplastic polyp （HP）,sessile serrated adenoma/polyp （SSA/P）,and traditional serrated adenoma （TSA） of all serrated polyps were 41.2%,7.2%,and 51.6%,respectively,which showed a lower proportion of HP and SSA/P and a higher proportion of TSA.Serrated polyps appeared more in males and elder patients while there was no significant difference in the subtype distribution in gender and age.The proportions of large and proximal serrated polyps were 13.7% （21/153） and 46.4% （71/153）,respectively.In total,98.9% （89/90） serrated adenomas were found with dysplasia.Moreover,14 patients with serrated polyps were found with synchronous advanced colorectal neoplasia,and large serrated polyps （LSPs） （odds ratio：3.446,95% confidence interval：1.010-11.750,P 〈 0.05）,especially large HPs,might have an association with synchronous advanced neoplasia （AN）.Conclusions：The overall detection rate ofcolorectal serrated polyps in Chinese symptomatic patient population was low,and distribution pattern of three subtypes is different from previous reports.Moreover,LSPs,especially large HPs,might be associated with an increased risk of synchronous AN.