subepithelial tumors ( sets ) of the gastrointestinal ( gi ) tract are sometimes encountered during routine esophagogastroduodenoscopy . it is essential to biopsy these lesions because there is always the possibility that some of it has malignant potential . biopsy is especially important to differentiate gi stromal tumors ( gists ) from other tumors . although endoscopic ultrasonography ( eus ) is the best imaging modality for the evaluation of various sets , pathological diagnosis is still necessary for an accurate diagnosis . there are several potential techniques for making a tissue diagnosis , including eus - guided fine - needle aspiration ( eus - fna ) biopsy , eus - guided trucut biopsy ( eus - tcb ) , and stacked biopsy . however , these techniques have limited diagnostic efficacy . although eus - fna is currently considered the standard diagnostic technique for gi sets , its diagnostic yield varies in the literature between 38% and 82% ( 123 ) . the diagnostic yields of eus - tcb are reported to be similar to those of eus - fna because of the high rate of technical failure of tcb ( 45 ) . forceps biopsy has a lower diagnostic yield than do eus - tcb and eus - fna ( roughly 17% to 38% ) ( 67 ) . endoscopic resection by snaring and submucosal dissection provides both pathological diagnosis and treatment for the tumor . however , this procedure can be technically difficult and demands a long procedure time , with a risk of perforation ( 8910111213 ) . set ligation with bands and loops has been proposed to reduce the risk of perforation during endoscopic removal . however , ligating these lesions is also technically demanding and does not provide an en bloc specimen for surgical pathology and margin evaluation ( 1415161718 ) . ultimately , it is not necessary to remove the entire lesion through endoscopic resection for diagnostic purposes alone . the goal of this study was to evaluate the diagnostic yield and safety of forceps biopsies after small endoscopic submucosal dissection ( sesd biopsies ) in the diagnosis of gastric sets and compare it with eus - fna . this was a study conducted at a tertiary referral center in korea ( kangbuk samsung hospital ) . patients who underwent sesd biopsies were prospectively enrolled between may 2013 and october 2014 if they had intramural gastric sets > 10 mm on eus . exclusion criteria included age < 18 years , thrombocytopenia ( platelet count < 100,000 cells/l ) , and lesions with typical sonographic features of a lipoma , varix , or cyst . such features included tumors > 30 mm in diameter and those with heterogeneous echo , cystic spaces , hyperechogenic foci , irregular margins , or adjacent malignant - appearing lymph nodes . these patients were recommended to have surgery for removal of a set ( 19 ) . antithrombotic agents were stopped five days prior to the procedure , and were restarted on the day after . to compare sesd biopsies with eus - fna , we used the retrospective data of 30 eus - fna cases which was performed for the diagnosis of gastric sets between april 2012 and february 2014 in the two centers ( kangbuk samsung hospital and samsung medical center ) . sesd biopsies were performed by two experienced endoscopists ( j.h.p . and y.s.j . ) , with patients under conscious sedation . sets were initially characterized with a radial scanning echoendoscope ( gf ue260 & um-3r miniprobe ; olympus , tokyo , japan ) . eus was used to measure set size by the maximum cross - section of the lesion . if eus confirmed that the intramural sets were > 10 mm , then sesd biopsies was performed immediately after eus by the same endoscopist who perform eus . therefore , sesd biopsies required only one anesthesia and only needed to change out endoscopes ( echoendoscope to conventional endoscope ) . 1 . a transparent cap ( distal attachment [ d-201 - 11304 ] ; olympus ) was fitted to the endoscope tip ( gif - h260 ; olympus ) . a telemed disposable sclerotherapy needle ( telemed systems , inc . , hudson , ma , usa ) was used to inject sets with a mixed solution of normal saline + 0.016% indigo carmine + 0.01% epinephrine . a dual knife ( electrosurgical knife [ kd-650l ] ; olympus ) connected to an electrosurgical unit ( erbe electromedizin , tbingen , germany ) was used to incise the lesion using the  endocut  mode ( effect 3 , cut duration 2 , cut interval 3 , and upmax 550 vp ) . a cross - shaped incision and dissection of 6 to 10 mm in size was made under direct endoscopic access over the lesion s highest convexity zone . a dual knife was used to incise the mucosa and submucosa , and then we confirmed that the underlying tumor was exposed . conventional biopsy forceps ( oval spoon - shaped mouth , without spike [ fenestrated , tapered ] ; mtw , dsseldorf , germany ) were then introduced deep into the lesion , and 27 samples were obtained . incisions were closed with 24 endoclips ( long clip [ hx-610 - 090l ] ; olympus ) . the biopsy specimens obtained were immediately placed in formalin and were submitted for histopathologic and immunohistochemical examination . when conventional cytologic analysis revealed features of mesenchymal origin , further differentiation into gist and non - gist was performed by immunohistochemical analysis of cd117 ( c - kit ) , cd34 , smooth muscle actin , and s-100 markers . ( d ) cross - shaped dissection of the mucosa and submucosa with a dual knife . ( f ) biopsy forceps were introduced through the hole , taking multiple tissue samples from inside . the participants also returned to the hospital within 24 weeks of their endoscopy to be evaluated for post - procedural adverse events . eus - fna was performed by using a linear echoendoscope ( gf - uct 260 ; olympus ) with a 19 or 22 gauge ( eusn3 echotip ; wilson - cook medical inc . , winston - salem , nc , usa ) according to standard techniques , under real - time us guidance and color / pulsed doppler control . the patients who underwent eus - fan were hospitalized and carefully monitored for 24 hours after the eus - fna . student s t - test was used to compare numerical variables between the two groups and the  or the fisher s exact test was used to compare categorical variables . the study protocol was approved by the institutional review board of kangbuk samsung hospital ( irb no . all patients who agreed to participate in the study signed a written informed consent form . this study has been registered with the clinical research information service ( cris ) , republic of korea ( clinical trial registration no . the study protocol was approved by the institutional review board of kangbuk samsung hospital ( irb no . all patients who agreed to participate in the study signed a written informed consent form . this study has been registered with the clinical research information service ( cris ) , republic of korea ( clinical trial registration no . sesd biopsies , as described , was attempted in 42 patients ( mean age 53 years ) and eus - fna was performed in 30 patients ( mean age 50 years ) . table 1 summarizes the demographic characteristics of patients and endoscopic characteristics of the gastric sets . the average lesion size measured with eus in sesd biopsies group was smaller than that in eus - fna group ( mean 18.8  5.9 mm vs. 32.2  12.0 mm , p < 0.001 ) . the set locations in sesd biopsies group included : cardia ( n = 9 , 21.4% ) , fundus ( n = 5 , 11.9% ) , gastric body ( n = 17 , 40.5% ) , and antrum ( n = 11 , 26.2% ) . the set locations in eus - fna group included : cardia ( n = 11 , 36.7% ) , fundus ( n = 2 , 6.7% ) , gastric body ( n = 16 , 53.3% ) , and antrum ( n = 1 , 3.3% ) . in sesd biopsies group , 2 patients ( 4.8% ) had lesions that arose from the muscularis mucosa , 14 ( 33.3% ) from the submucosa , and 26 ( 61.9% ) from the muscularis propria , whereas in eus - fna group , only one patient ( 3.3% ) had lesion that arose from the muscularis mucosa and all the other ( 96.7% ) from the muscularis propria ( p = 0.002 ) . hypoechoic and homogenous lesions were more frequent in eus - fna group than in sesd biopsies group . sesd biopsies = forceps biopsies after small endoscopic submucosal dissection , eus - fna = endoscopic ultrasonography - guided fine - needle aspiration . the diagnostic yield of sesd biopsies was comparable to that of eus - fna ( 35 of 42 , 83.3% vs. 24 of 30 , 80.0% , p = 0.717 ) ( table 2 ) . in addition , the diagnostic yield of sesd biopsies was comparable to that of eus - fna among lesions originated from muscularis propria layer ( 21 of 26 , 80.8% vs. 24 of 29 , 82.8% , p = 1.000 ) . in sesd biopsies group , the diagnostic lesions included 15 leiomyomas , 7 gists , 10 heterotopic pancreases , 2 lipomas , and one other lesion . the other lesion was an 18-mm isoechoic , heterogeneous mass that originated from the submucosal layer . pathological analysis of this lesion revealed tiny pieces of fibrovascular tissue with mucinous material suggestive of mucin containing benign lesions or mucinous adenocarcinoma . esd confirmed the pathological diagnosis of mucinous adenocarcinoma with invasion into the submucosa ( sm 3 ) . in eus - fna group , the diagnostic lesions included 11 leiomyomas , 14 gists , and 1 neuroendocrine tumor . sesd biopsies = forceps biopsies after small endoscopic submucosal dissection , eus - fna = endoscopic ultrasonography - guided fine - needle aspiration , gist = gastrointestinal stromal tumors . the mean numbers of forceps biopsies in sesd biopsies group was 3.9 and needle passes in eus - fna group were 3.3 ( p = 0.021 ) . the mean procedure time of sesd biopsies was shorter than that of eus - fna ( 10 vs. 37 minutes , p < 0.001 ) . , there was a small amount of bleeding from the cut surface immediately after incision of the overlying mucosa and submucosa or from the tumor surface after biopsy . there were no procedure - related adverse events including perforation or massive bleeding in both groups . the results of seven gist cases in sesd biopsies group are shown in table 3 . the forceps biopsy specimens obtained from these cases were not large enough to evaluate the mitotic index in 50 consecutive high power fields ( hpfs ) ( range 542 hpfs ) . of the seven patients with gist , four underwent a surgical resection . according to fletcher s classification , three of these four patients were classified to be at very low risk for a malignancy and only one patient was at intermediate risk ( 20 ) . sesd biopsies = forceps biopsies after small endoscopic submucosal dissection , eus = endoscopic ultrasonography , gist = gastrointestinal stromal tumors , hpf = high power field , na = not available . among sesd biopsies group in addition , there were no significant differences between the diagnostic and nondiagnostic cases with regard to set size , location , originating layer , and the number of forceps biopsies obtained ( table 4 ) . sesd biopsies = forceps biopsies after small endoscopic submucosal dissection , eus = endoscopic ultrasonography . it is important to differentiate the various types of sets because these lesions have different prognoses and require different management or therapeutic options . eus findings alone have limited specificity for the diverse subtypes of sets and fail to distinguish between benign and malignant lesions . our study demonstrated that the diagnostic yield of sesd biopsies was comparable to that of eus - fna ( 83% vs. 80% ) . currently , there is no consensus regarding the optimal management strategy for small ( < 3 cm in diameter ) asymptomatic sets . a recent update in the national comprehensive cancer network guidelines on the management of gists recommended that incidentally encountered small gists ( < 2 cm in diameter ) be followed endoscopically until they grow or become symptomatic ( 21 ) . another study reported that gist lesions ( diagnosed by eus ) that are < 3 cm in size with low malignant potential can be observed with eus rather than cytohistologically diagnosed or removed ( 19 ) . however , current literature suggests that all gist lesions have malignant potential , even those just 1 cm in size ( 22 ) . therefore , optimal pathologic examination of tumor tissue is mandatory , especially for lesions that are hypoechoic , located in the muscularis propria of the stomach , or are > 2 cm . eus - fna is currently considered the standard method for gi sets samples ; however , it has limited value for the cytologic diagnosis of nonmesenchymal lesions ( with nondiagnostic samples up to 100% ) ( 3 ) . in addition , eus - fna has a high failure rate in immunostaining with regard to mesenchymal tumors ; this limitation decreases its diagnostic yield from 70%74% to 34%53% after immunohistochemical analysis ( 34 ) . unfortunately , immunohistochemical analysis is not always feasible with eus - fna samples because there is insufficient material obtained by aspiration . eus - tcb emerged as a method to solve the limitations of eus - fna . theoretically , this procedure provides core - tissue specimens that would increase the diagnostic yield with thicker samples . despite this prediction , the diagnostic yield of tcb in gi sets is not superior to that of eus - fna ( 47%63% ) ( 4523 ) . there is a high rate of technical failure with tcb because the device is very stiff , which hinders the needle from obtaining tissue ( 24 ) . a previous study reported that among 52 tcb procedures performed for gastric sets , there were two cases of sepsis ( 5 ) . this study presents several reasons why sesd biopsies may be preferable to eus - fna or eus - tcb . although its diagnostic yield was compared to the retrospective data of eus - fna cases , our results show that its diagnostic yield is not inferior to that of eus - fna . second , sesd biopsies also provide sufficient tissue for accurate diagnosis in a cost - effective manner , while avoiding unnecessary follow - up examinations or repeated exploratory surgeries . according to our data , the pathological diagnoses of 35 included 7 gists , 15 leiomyomata , and 10 heterotopic pancreases . patients who were diagnosed with benign lesions such as a leiomyoma or heterotopic pancreas do not require annual eus examinations or surgical resection . third , another advantage to sesd biopsies is that it can be easily performed regardless of the lesion s anatomic location . in contrast , eus - fna and eus - tcb have high failure rates with regard to tissue acquisition when the set lesion is in the cardia or fundus because the stiff device has difficulty accessing these areas . the diagnostic yield of sesd biopsies is high , even when sets are in the cardia or fundus ( 13 of 14 , 93% ) . our results showed that the average lesion size in sesd biopsies group was smaller than that in eus - fna group ( 19 vs. 32 mm ) . fifth , sesd biopsy is a safe procedure . there were no procedure - related adverse events in this study including perforation , bleeding , or sepsis . finally , the procedure time of sesd biopsies was shorter than that of eus - fna ( 10 vs. 39 minutes ) and thus it can save time . similarly to eus - fna and eus - tcb , the main limitation of the sesd biopsies is that it does not provide sufficient tissue ( with at least 50 hpfs ) to evaluate the malignant potential of gists . if more forceps biopsies are performed , it is possible to obtain 50 consecutive hpfs in order to evaluate the mitotic index . however , biopsy - obtained tissue is unlikely to represent the mitotic activity of the entire tumor . the mitotic index measured over 50 hpfs may actually be inaccurate because of the heterogeneous distribution of mitotic activity . in addition , the mitotic index should be measured from the most mitotically active area . another group recently developed us - guided single - incision with needle knife ( sink ) and deep forceps biopsy for the histologic diagnosis of upper gi sets ( 25 ) . they found that the diagnostic yield of the sink biopsy was 92.8% ( 13 of 14 ) . of eight gist cases , the sink specimens were sufficient for immunohistochemical analysis in seven cases and for measurement of the mitotic index in five cases . the diagnostic yield of our method was not superior to that of the sink biopsy ( 83.3% vs. 92.8% ) . however , our study included a larger number of patients than did the sink biopsy study ( 42 vs.14 cases ) . our methods involved a cross - shaped dissection of mucosa and submucosa , exposure of the underlying tumor , and then tissue extraction through the forceps biopsy . in contrast , the sink biopsy involves a linear incision without confirming the exposure of the underlying tumor . although sink specimens allowed the evaluation of the mitotic index in some of gist cases , this index may not represent the entire tumor , as described previously . their procedure involved making a 5-mm - diameter hole with a flex knife and then a 15-mm - diameter round incision . next , they used an it2 knife to make a submucosal dissection and performed multiple endoscopic biopsies . this technique is somewhat inconvenient because it employs both a flex knife and an it2 knife , as opposed to our method , which only required a dual knife . recently , several diagnostic methods using the unroofing technique have been proposed to obtain a sufficient amount of gi set tissue . these techniques include partial resection ( 27 ) , retract - ligate - unroof - biopsy with loop ( 17 ) , and suck - ligate - unroof - biopsy by using loop ( 18 ) . these methods have high diagnostic yields ( 94% , 81% , and 100% , respectively ) and provide sufficient tumor tissue for immunohistochemical analysis and mitotic index calculation . however , incomplete endoscopic resection of a gist tumor can allow for peritoneal dissemination of disease ( 11 ) . furthermore , the retract - ligate - unroof - biopsy and suck - ligate - unroof - biopsy with loop techniques can not provide an en bloc specimen of the entire tumor or negative margin assessment ; therefore , any neoplastic lesion with malignant potential needs close serial follow - up by expensive eus . an unexpected finding in our study is that leiomyoma was the most common gastric set ( although non - diagnostic lesions were considered ) . gist is known to be the most frequent set in the stomach , whereas leiomyoma is the most frequent set in the esophagus ( 28 ) . in our study , among sesd biopsies group , most sets ( 8 of 9 ) in the cardia were leiomyomas and only one case was heterotopic pancreas . if a set > 20 mm is incidentally found during routine endoscopy in the cardia of the stomach , there is high probability that it is a leiomyoma . first , the sample size was small and sesd biopsies were performed at a single center by only two endoscopists . it is possible that the operator - related factors influenced our results and that the diagnostic yields may be lower than those in an average practice . future investigation at multiple centers with more endoscopists is needed to clarify the efficacy of sesd biopsies . another limitation to this study is that the diagnostic yield of sesd biopsies was compared to the retrospective data of eus - fna cases . finally , sesd biopsies specimens were not large enough to evaluate mitotic index in 50 consecutive hpfs . this study focused on the acquisition of tissue specimens with sesd biopsies for diagnostic purposes . sesd biopsies was found to be an effective , easy , and safe technique for the histologic diagnosis of gastric sets and its diagnostic yield is comparable to that of eus - fna . however , further prospective comparative studies with larger sample sizes are needed to confirm this method s efficacy .
the current tissue sampling techniques for subepithelial tumors ( sets ) of the gastrointestinal ( gi ) tract have limited diagnostic efficacy . 
 we evaluated the diagnostic yield and safety of forceps biopsies after small endoscopic submucosal dissection ( sesd biopsies ) in the diagnosis of gastric sets . 
 a total of 42 patients with gastric sets > 10 mm were prospectively enrolled between may 2013 and october 2014 . 
 a dual knife was used to incise the mucosa and submucosa and forceps biopsies were then introduced deep into the lesion . to compare sesd biopsies with eus - fna , we used the retrospective data of 30 eus - fna cases . 
 the diagnostic yield of sesd biopsies was comparable to that of eus - fna ( 35/42 , 83.3% vs. 24/30 , 80.0% , p = 0.717 ) . 
 the mean procedure time of sesd biopsies was shorter than that of eus - fna ( 10 vs. 37 minutes , p < 0.001 ) . 
 there were no procedure - related adverse events in the both group . 
 the pathological diagnoses in sesd biopsies group included 15 leiomyomas , 7 gists , 10 heterotopic pancreases , 2 lipomas , and one other lesion . 
 sesd biopsies are an easy , effective and safe technique for the diagnosis of gastric sets and its diagnostic yield is comparable to that of eus - fna . this technique may be a reliable alternative to conventional eus - fna ( clinical trial registration no . 
 kct0000730 ) .