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.     

Endoscopic and histologic characteristics of serrated lesions

In recent years , a second pathway for colonic carcinogenesis , distinct from the adenomatous pathway, has been explored. This is referred to as serrated pathway and includes three types of polyp,characterised by a serrated appearance of the crypts:hyperplastic polyps(HP),sessile serrated adenomas(SSA)or lesions,and traditional serrated adenomas.Each lesion has its own genetic,as well as macroscopic and microscopic morphological features.Because of their flat aspect,their detection is easier with chromoendoscopy(carmin indigo or narrow-band imaging).However,as we show in this review,the distinction between SSA and HP is quite difficult.It is now recommended to resect in one piece as it is possible the serrated polyps with a control in a delay depending on the presence or not of dysplasia.These different types of lesion are described in detail in the present review in general population,in polyposis and in inflammatory bowel diseases patients.This review highlights the need to improve characterization and understanding of this way of colorectal cancerogenesis.     

Serrated pathway in colorectal carcinogenesis

Serrated adenocarcinoma is a recently described subset of colorectal cancer(CRC),which account for about10%of all CRCs and follows an alternative pathway in which serrated polyps replace the traditional adenoma as the precursor lesion to CRC.Serrated polyps form a heterogeneous group of colorectal lesions that includes hyperplastic polyps(HPs),sessile serrated adenoma(SSA),traditional serrated adenoma(TSA)and mixed polyps.HPs are the most common serrated polyp followed by SSA and TSA.This distinct histogenesis is believed to have a major influence in prevention strategies,patient prognosis and therapeutic impact.Genetically,serrated polyps exhibited also a distinct pattern,with KRAS and BRAF having an important contribution to its development.Two other molecular changes that have been implicated in the serrated pathway include microsatellite instability and the CpG island methylator phenotype.In the present review we will address the current knowledge of serrated polyps,clinical pathological features and will update the most recent findings of its molecular pathways.The understanding of their biology and malignancy potential is imperative to implement a surveillance approach in order to prevent colorectal cancer development.     

Heterogeneity of colorectal adenomas, the serrated adenoma, and implications for screening and surveillance

Current algorithms for screening and surveillance for colon cancer are valuable, but may be limited by the underlying nature of the targeted neoplastic lesions. Although part of the success of adenoma removal relates to interruption of so-called ＂adenoma-carcinoma sequence＂, an alternate serrated pathway to colon cancer may pose difficulties with the ultimate results achieved by traditional colonoscopic methods. The endpoint carcinoma in this unique pathway may be derived from a dysplastic serrated adenoma. These tend to be located primarily in the right colon, especially in females, and are frequently associated with co-existent colon cancer. Unfortunately, however, there are few, if any, other identifiable risk factors, including age or family history of colon polyps or colon cancer. Moreover, this alternate serrated pathway may itself also be quite biologically heterogeneous as reflected in sessile serrated adenomas （SSA） with virtually exclusive molecular signatures defined by the presence of either BRAF or KRAS mutations. Screening algorithms in the future may need to be modified and individualized, depending on new information that likely will emerge on the natural history of these biologically heterogeneous lesions that differs from traditional adenomatous polyps.     

Serrated polyps of the colon and rectum: Endoscopic features including image enhanced endoscopy

In this review, I outline the characteristic endoscopic findings of serrated lesions of the colorectum based on image enhanced endoscopy(IEE). Histopathologically, lesions with serrated structures are typically classified into the following three types based: hyperplastic polyps(HPs), traditional serrated adenomas(TSAs), and sessile serrated adenoma/polyps(SSA/Ps). Both HP and SSA/P often present as dark-green colors on auto fluorescence imaging(AFI) colonoscopy that are similar to the normal surrounding mucosa. In contrast, TSAs often have elevated shapes and present as magenta colors that are similar to the tubular adenomas. The superficial type of TSA also includes many lesions that present as magenta colors. When SSA/Ps are associated with cytological dysplasia, many lesions present with magenta colors, whereas lesions that are not associated with cytological dysplasia present with dark-green colors. When observed via narrow band imaging(NBI), many SSA/P include lesions with strong mucous adhesions. Because these lesions are observed with reddish mucous adhesions, we refer to them as "red cap sign" and place such signs among the typical findings of SSA/P. Because the dilatation of the pit in SSA/P is observed as a round/oval black dot on magnified observations, we refer to this finding as Ⅱ-dilatation pit(Ⅱ-D pit) and also positioned it as a characteristic finding of SSA/P. In contrast, dilatations of the capillary vessels surrounding the glands, such as those that occur in tubular adenoma, are not considered to be useful for differentiating HPs from SSA/Ps. However, in cases in which SSA/P is associated with cytological dysplasia, the dilatation of capillary vessels is observed in the same area. When submucosal layer invasion occurs in the same area, the blood flow presents with irregularities that are similar to those of common colorectal cancer at an early stage and disappears as the invasion proceeds deeply. The surface pattern of invasive cancer that is observed at the tumor surface is also likely to disappear. Based on the above results, we considered that the differentiations between HP and TSA, between TSA and SSA/P, and between HP and SSA/P might become easier due to the concomitant use of white light observation and IEE. We also concluded that AFI and NBI can be useful modalities for SSA/P lesions associated with cytological dysplasia.     

Serrated pathway:Alternative route to colorectal cancer

Serrated polyps have been an area of intense focus for gastroenterologists over the past several years. Contrary to what was thought before,a growing body of literature indicates that these polyps can be precursors of colorectal cancer(CRC).Most of these lesions, particularly those in the proximal colon,have so far been under-recognized and missed during colonoscopy,qualifying these lesions to be the main cause of interval cancers.It is estimated that 10%-20%of CRCs evolve through this alternative,serrated pathway, with a distinct genetic and epigenetic profile.Aberrant DNA methylation plays a central role in the development of this CRC subtype.This characteristic molecular background is reflected in a unique pathological and clinical manifestation different from cancers arising via the traditional pathway.In this review we would like to highlight morphological,molecular and clinical features of this emerging pathway that are essential for gastroenterologists and may influence their everyday practice.     

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.     

BRAF, K-ras and BAT26 mutations in colorectal polyps and stool

AIM: To assess the feasibility of using BRAF, K-ras and BAT26 genes as stool-based molecular markers for detection of colorectal adenomas and hyperplastic polyps (HPs). METHODS: We applied PCR-SSCP and direct sequencing to detect BRAF mutations of polyps and paired stool samples. Primer-mediated restriction fragment length polymorphism (RFLP) analysis and mutant-enriched PCR were used in detection of K-ras mutations of polyp tissues and paired stool samples respectively. BAT26, a microsatellite instability marker was examined by detection of small unstable alleles in a poly (A) repeat. RESULTS: No genetic alterations were detected in the 36 colonoscopically normal patients in either tissues or stools. BRAF, K-ras and BAT26 mutations were found in 4 (16%), 10 (40%) and 3 (12%) of 25 adenoma tissues and among them, 75%, 80% and 100% of patients were observed to contain the same mutations in their corresponding stool samples. In HPs, mutations of BRAF and K-ras were detected in the tumor DNA of 2 (11.1%) and 8 (33.3%) of 18 patients respectively, all of whom had identical alterations in their stools. Taken together, the three genetic markers detected 15 (60%) of 25 adenomas and 8 (44.4%) of 18 HPs. The sensitivity of stool detection was 80% for adenomas and 100% for HPs with an overall specificity of 92% for adenomas and 100% for HPs. CONCLUSION: BRAF, K-ras and BAT26 genes have the potential to be molecular markers for colorectal adenomas and HPs, and can be used as non-invasive screening markers for colorectal polyps.     

Clinical features of upper gastrointestinal serrated lesions: An endoscopy database analysis of 98746 patients

AIM To analyse the clinical features of patients with the serrated lesions in the upper gastrointestinal tract(UPGI) tract.METHODS Patients who underwent routine esophagogastroduodenoscopy(EGD) at the Digestive Endoscopy Centre of General Hospital, Tianjin Medical University between january 2011 and December 2015 were consecutively recruited. Patients with UPGI serrated lesions were consecutively identified. The patients' demographics and histopathology were recorded. The colorectal findings for patients who underwent colonoscopy simultaneously or within six months were also extracted from the colonoscopy database. In addition, we analyseddifferences in colorectal neoplasia detection between the study patients and randomly selected patients matched for age and gender who did not exhibit serrated lesions and who also underwent colonoscopy in the same period.RESULTS A total of 21 patients out of 98746 patients(0.02%) who underwent EGD were confirmed to have serrated lesions with predominantly crenated, sawtooth-like configurations. The mean age of the 21 patients was(55.3 ± 17.2) years, and 11 patients were male(52.4%). In terms of the locations of the serrated lesions, 17 were found in the stomach(including 3 in the cardia, 9 in the corpus and 5 in the antrum), 3 were found in the duodenum, and 1 was found in the esophagus. Serrated lesions were found in different mucosal lesions, with 14 lesions were detected in polyps(8 hyperplastic polyps and 6 serrated adenomas with low grade dysplasia), 3 detected in Ménétrier gastropathy, 3 detected in an area of inflammation or ulcer, and 1 detected in the intramucosal carcinoma of the duodenum. In addition, colonoscopy data were available for 18 patients, and a significantly higher colorectal adenoma detection rate was observed in the UPGI serrated lesions group than in the randomly selected age- and gender-matched group without serrated lesions who also underwent colonoscopy in the same period(38.9% vs 11.1%, OR = 5.091, 95%CI: 1.534-16.890, P = 0.010). The detection rate of advanced adenoma was also higher in the UPGI serrated lesions group(22.2% vs 4.2%, OR = 6.571, 95%CI: 1.322-32.660, P = 0.028).CONCLUSION Serrated lesions in the UPGI were detected in various mucosal lesions with different pathological morphologies. Moreover colonoscopy is recommended for the detection of concurrent colorectal adenoma for these patients.     

IGF2 differentially methylated region hypomethylation in relation to pathological and molecular features of serrated lesions

AIM:To investigate insulin-like growth factor 2(IGF2)differentially methylated region(DMR)0 hypomethylation in relation to clinicopathological and molecular features in colorectal serrated lesions.METHODS:To accurately analyze the association between the histological types and molecular features of each type of serrated lesion,we consecutively collected1386 formalin-fixed paraffin-embedded tissue specimens that comprised all histological types[hyperplastic polyps(HPs,n=121),sessile serrated adenomas(SSAs,n=132),traditional serrated adenomas(TSAs,n=111),non-serrated adenomas(n=195),and colorectal cancers(n=827)].We evaluated the methylation levels of IGF2 DMR0 and long interspersed nucleotide element-1(LINE-1)in HPs(n=115),SSAs(n=120),SSAs with cytological dysplasia(n=10),TSAs(n=91),TSAs with high-grade dysplasia(HGD)(n=15),non-serrated adenomas(n=80),non-serrated adenomas with HGD(n=105),and CRCs(n=794).For the accurate quantification of the relative methylation levels(scale 0%-100%)of IGF2 DMR0 and LINE-1,we used bisulfite pyrosequencing method.Tumor specimens were analyzed for microsatellite instability,KRAS(codons 12 and 13),BRAF(V600E),and PIK3CA(exons 9and 20)mutations;MLH1 and MGMT methylation;and IGF2 expression by immunohistochemistry.RESULTS:The distribution of the IGF2 DMR0 methylation level in 351 serrated lesions and 185 non-serrated adenomas(with or without HGD)was as follows:mean61.7,median 62.5,SD 18.0,range 5.0-99.0,interquartile range 49.5-74.4.The IGF2 DMR0 methylation level was divided into quartiles(Q1≥74.5,Q2 62.6-74.4,Q3 49.6-62.5,Q4≤49.5)for further analysis.With regard to the histological type,the IGF2 DMR0 methylation levels of SSAs(mean±SD,73.1±12.3)were significantly higher than those of HPs(61.9±20.5),TSAs(61.6±19.6),and non-serrated adenomas(59.0±15.8)(P<0.0001).The IGF2 DMR0 methylation level was inversely correlated with the IGF2 expression level(r=-0.21,P=0.0051).IGF2 DMR0 hypomethylation was less frequently detected in SSAs compared with HPs,TSAs,and non-serrated adenomas(P<0.0001).Multivariate logistic regression analysis also showed that IGF2 DMR0 hypomethylation was inversely associated with SSAs(P<0.0001).The methylation levels of IGF2 DMR0 and LINE-1 in TSAs with HGD(50.2±18.7and 55.7±5.4,respectively)were significantly lower than those in TSAs(61.6±19.6 and 58.8±4.7,respectively)(IGF2 DMR0,P=0.038;LINE-1,P=0.024).CONCLUSION:IGF2 DMR0 hypomethylation may be an infrequent epigenetic alteration in the SSA pathway.Hypomethylation of IGF2 DMR0 and LINE-1 may play a role in TSA pathway progression.     

Different standards for healthy screenees than patients in routine clinics?

Less than 5%of colorectal adenomas will become malignant,but we do not have sufficient knowledge about their natural course to target removal of these5%only.Thus,95%of polypectomies are a waste of time exposing patients to a small risk of complications.Recently,a new type of polyps,sessile serrated polyps,has attracted attention.Previously considered innocuous,they are now found to have molecular similarities to cancer and some guidelines recommend to have them removed.These lesions are often flat,covered by mucous,not easily seen and situated in the proximal colon where the bowel wall is thinner.Thus,polypectomy carries a higher risk of perforation than predominantly left-sided,stalked adenomas-and we do not know what is gained in terms of cancer prevention.Screening is a neat balance between harms and benefit for presumptively healthy participants not interested in risk exposure to obtain confirmation of being healthy.The situation is quite different for patient worried about symptom.Thus,the standards set for evidence-based practice may be higher for screening than for routine clinics-a mechanism which may benefit patients in the long run.     

Endoscopic mucosal resection in the upper gastrointestinal tract

Endoscopic mucosal resection （EMR） is a technique used to locally excise lesions confined to the mucosa. Its main role is the treatment of advanced dysplasia and early gastrointestinal cancers. EMR was originally described as a therapy for early gastric cancer. Recently its use has expanded as a therapeutic option for ampullary masses, colorectal cancer, and large colorectal polyps. In the Western world, the predominant indication for EMR in the upper gastrointestinal tract is the staging and treatment of advance dysplasia and early neoplasia in Barrett＇s esophagus. This review will describe the basis, indications, techniques, and complications of EMR, and its role in the management of Barrett＇s esophagus.     

Endoscopic diagnosis of sessile serrated adenoma/polyp with and without dysplasia/carcinoma

Sessile serrated adenoma/polyps(SSA/Ps) are early precursor lesions in the serrated neoplasia pathway, which results in colorectal carcinomas with BRAF mutations, methylation for DNA repair genes, a Cp G island methylator phenotype, and high levels of microsatellite instability. Some of these lesions can rapidly become dysplastic or invasive carcinomas that exhibit high lymphatic invasion and lymph node metastasis potentials. Detecting serrated lesions, including SSA/Ps with and without dysplasia/carcinoma, is critical, but SSA/Ps can be difficult to detect, are inconsistently identified by endoscopists and pathologists, and are often incompletely resected. Therefore, SSA/Ps are considered to be major contributors to "interval cancers". If colonoscopists can identify the specific endoscopic characteristics of SSA/Ps, their detection and the effectiveness of colonoscopy may improve. Here, the endoscopic features of SSA/Ps with and without dysplasia/carcinoma, including the characteristics determined using magnifying endoscopy, are reviewed in the context of previous reports. Endoscopically, these subtle polyps are like hyperplastic polyps, because they are slightly elevated and pale. Unlike hyperplastic polyps, SSA/Ps are usually larger than 5 mm, frequently covered by a thin layer called the ‘‘mucus cap', and are more commonly located in the proximal colon. Magnifying narrow-band imaging findings, which include dark spots inside the crypts and varicose microvascular vessels, in addition to the type II-open pit patterns detected using magnifying chromoendoscopy, effectively differentiate SSA/Ps from hyperplastic polyps. The lesions' endoscopic characteristics, which include their(semi)pedunculated morphologies, double elevations, central depressions, and reddishness, and the use of magnifying endoscopy, might help to detect dysplasia/carcinoma within SSA/Ps. Greater awareness may promote further research into improving the detection, identification, and complete resection rates of SSA/Ps with and without dysplasia/carcinoma and reduce the interval cancer rates.     

Endoscopic resection techniques for colorectal neoplasia:Current developments

Endoscopic polypectomy and endoscopic mucosal resection(EMR) are the established treatment standards for colorectal polyps. Current research aims at the reduction of both complication and recurrence rates as well as on shortening procedure times. Cold snare resection is the emerging standard for the treatment of smaller(< 5 mm) polyps and is possibly also suitable for the removal of noncancerous polyps up to 9 mm. The method avoids thermal damage, has reduced procedure times and probably also a lower risk for delayed bleeding. On the other end of the treatment spectrum, endoscopic submucosal dissection(ESD)offers en bloc resection of larger flat or sessile lesions. The technique has obvious advantages in the treatment of high-grade dysplasia and early cancer. Due to its minimal recurrence rate, it may also be an alternative to fractionated EMR of larger flat or sessile lesions. However, ESD is technically demanding and burdened by longer procedure times and higher costs. It should therefore be restricted to lesions suspicious for high-grade dysplasia or early invasive cancer.The latest addition to endoscopic resection techniques is endoscopic fullthickness resection with specifically developed devices for flexible endoscopy.This method is very useful for the treatment of smaller difficult-to-resect lesions,e.g., recurrence with scar formation after previous endoscopic resections.     

Folic acid supplementation inhibits recurrence of colorectal adenomas： A randomized chemoprevention trial

AIM： To determine whether folic acid supplementation will reduce the recurrence of colorectal adenomas, the precursors of colorectal cancer, we performed a double-blind placebo-controlled trial in patients with adenomatous polyps.
METHODS： In the current double-blind, placebocontrolled trial at this VA Medical Center, patients with colorectal adenomas were randomly assigned to receive either a daily 5 mg dose of folic acid or a matched identical placebo for 3 years. All polyps were removed at baseline colonoscopy and each patient had a follow up colonoscopy at 3 years. The primary endpoint was a reduction in the number of recurrent adenomas at 3 years.
RESULTS： Of 137 subjects, who were eligible after confirmation of polyp histology and run-in period to conform compliance, 94 completed the study; 49 in folic acid group and 45 in placebo group. Recurrence of adenomas at 3-year was compared between the two groups. The mean number of recurrent polyps at 3-year was 0.36 （SD, 0.69） for folic acid treated patients compared to 0.82 （SD, 1.17） for placebo treated subjects, resulting in a 3-fold increase in polyp recurrence in the placebo group. Patients below 70 years of age and those with left-sided colonic adenomas or advanced adenomas responded better to folic acid supplementation.
CONCLUSION： High dose folic acid supplementation is associated with a significant reduction in the recurrence of colonic adenomas suggesting that folic acid may be an effective chemopreventive agent for colorectal neoplasia.     

Synchronous colorectal cancer: Clinical,pathological and molecular implications

Synchronous colorectal carcinoma refers to more than one primary colorectal carcinoma detected in a single patient at initial presentation.A literature review has shown that the prevalence of the disease is approximately 3.5%of all colorectal carcinomas.This disease has a male to female ratio of 1.8:1.The mean age at presentation of patients with synchronous colorectal cancer is in the early half of the seventh decade.Patients with inflammatory bowel diseases(ulcerative colitis and Crohn’s disease),hereditary non-polyposis colorectal cancer,familial adenomatous polyposis and serrated polyps/hyperplastic polyposis are known to have a higher risk of synchronous colorectal carcinoma.These predisposing factors account for slightly more than 10%of synchronous colorectal carcinomas.Synchronous colorectal carcinoma is more common in the right colon when compared to solitary colorectal cancer.On pathological examination,some synchronous colorectal carcinomas are mucinous adenocarcinomas.They are usually associated with adenomas and metachronous colorectal carcinomas.Most of the patients with synchronous colorectal cancer have two carcinomas but up to six have been reported in one patient.Patients with synchronous colorectal carcinoma havea higher proportion of microsatellite instability cancer than patients with a solitary colorectal carcinoma.Also,limited data have revealed that in many synchronous colorectal carcinomas,carcinomas in the same patient have different patterns of microsatellite instability status,p53 mutation and K-ras mutation.Overall,the prognosis of patients with synchronous colorectal carcinoma is not significantly different from that in patients with solitary colorectal carcinoma,although a marginally better prognosis has been reported in patients with synchronous colorectal carcinoma in some series.A different management approach and long-term clinical follow-up are recommended for some patients with synchronous colorectal cancer.     

Malignant colorectal polyps

Nowadays, the number of cases in which malignant colorectal polyps are removed is increasing due to colorectal cancer screening programmes. Cancerous polyps are classified into non-invasive high grade neoplasia (NHGN), when the cancer has not reached the muscularis mucosa, and malignant polyps, classed as T1, when they have invaded the submucosa. NHGN is considered cured with polypectomy, while the prognosis for malignant polyps depends on various morphological and histological factors. The prognostic facto...     

Sessile serrated adenomas in the proximal colon are likely to be flat,large and occur in smokers

AIM:To examine the epidemiology and the morphology of the proximal sessile serrated adenomas(SSAs).METHODS:We conducted a retrospective study to identify patients with SSAs using a university-based hospital pathology database query from January 2007to April 2011.Data collected included:age,gender,ethnicity,body mass index,diabetes,smoking,family history of colorectal cancer,aspirin,and statin use.We collected data on morphology of SSAs including site(proximal or distal),size,and endoscopic appearance(flat or protuberant).We also compared proximal SSAs to proximal tubular adenomas detected during same time period.RESULTS:One hundred and twenty patients with SSAs were identified:61%were distal and 39%were proximal SSAs.Proximal SSAs were more likely to be flat than distal(100%vs 78%respectively;P=0.0001).Proximal SSAs were more likely to occur in smokers(OR=2.63;95%CI:1.17-5.90;P=0.02)and in patients with family history of colorectal cancer(OR=4.72;95%CI:1.43-15.55;P=0.01)compared to distal.Proximal SSAs were statistically more likely to be≥6 mm in size(OR=2.94;P=0.008),and also more likely to be large(≥1 cm)(OR=4.55;P=0.0005)compared to the distal lesions.Smokers were more likely to have proximal(P=0.02),flat(P=0.01)and large(P=0.007)SSAs compared to non-smokers.Compared to proximal tubular adenomas,proximal SSAs were more likely to be large and occur in smokers.CONCLUSION:Proximal SSAs which accounted for two-fifths of all SSAs were more likely to present as flat lesions,larger SSAs,and were more likely to occur in smokers and in patients with family history of colorectal cancer.Our data has implications for colorectal cancer screening.     

Difficult colon polypectomy

Colorectal cancer (CRC) is one of the leading causes of death from cancer in the world. We now know that 90% of CRC develop from adenomatous polyps. Polypectomy of colon adenomas leads to a significant reduction in the incidence of CRC. At present most of the polyps are removed endoscopically. The vast majority of colorectal polyps identified at colonoscopy are small and do not pose a significant challenge for resection to an appropriately trained and skilled endoscopist. Advanced polypectomy techniques are intended for the removal of difficult colon polyps. We have defined a "difficult polyp" as any lesion that due to its size, shape or location represents a challenge for the colonoscopist to remove. Although many "difficult polyps" will be an easy target for the advanced endoscopist, polyps that are larger than 15 mm, have a large pedicle, are flat and extended, are difficult to see or are located in the cecum or any angulated portion of the colon should be always considered difficult. Although very successful,advanced resection techniques can potentially cause serious, even life-threatening complications. Moreover, post polypectomy complications are more common in the presence of difficult polyps. Therefore, any endos-copist attempting advanced polypectomy techniques should be adequately supervised by an expert or have an excellent training in interventional endoscopy. This review describes several useful tips and tricks to deal with difficult polyps.     

Efficacy, risk factors and complications of endoscopic polypectomy： Ten year experience at a single center

AIM： To examine the efficacy and complications of colonoscopic resection of colorectal polypoid lesions. METHODS： We retrospectively reviewed 1354 polypectomies performed on 1038 patients over a ten- year period. One hundred and sixty of these were performed for large polyps, those measuring ≥ 20 mm. Size, shape, location, histology, the technique of polypectomy used, complications, drugs assumption and associated intestinal or extra intestinal diseases were analyzed. For statistical analysis, the Pearson χ2 test, NPC test and a Binary Logistic Regression were used. RESULTS： The mean patient age was 65.9 ± 12.4 years, with 671 men and 367 women. The mean size of polyps removed was 9.45 ± 9.56 mm while the size of large polyps was 31.5 ± 10.8 mm. There were 388 pedunculated and 966 sessile polyps and the most common location was the sigmoid colon （41.3%）. The most frequent histology was tubular adenoma （55.9%） while for the large polyps was villous （92/160 -57.5%）. Coexistent malignancy was observed in 28 polyps （2.1%） and of these, 20 were large polyps. There were 17 procedural bleeding （1.3%） and one perforation. The statistical analysis showed that cancer is correlated to polyp size （P 〈 0.0001）; sessile shape （P 〈 0.0001） and bleeding are correlated to cardiac disease （P = 0.034）, tubular adenoma （P = 0.016） and polyp size.CONCLUSION： The endoscopic resection is a simple and safe procedure for removing colon rectal neoplastic lesions and should be considered the treatment of choice for large colorectal polyps. The polyp size is an important risk factor for malignancy and for bleeding.