self - expandable metallic stents ( sems ) are now widely used to treat malignant colonic obstruction 1 
 2 
 3 . in cases involving the bridge to surgery strategy
, it is ideal to investigate the entire colon before surgery because the proportion of synchronous cancers in cases of obstructive colorectal cancer is 4  % to 6  % 4 
 5 .  
several studies have reported the effectiveness and safety of preoperative complete colonoscopy ( defined as a total colonoscopy via the use of stents ) after sems placement 5 
 6 
 7 .
preoperative complete colonoscopy has a great advantage in that , if a synchronous colorectal cancer is found , the surgical strategy can be altered to avoid multiple - stage operations .
although complete colonoscopy after sems placement has been recognized to be feasible and safe , the feasibility of endoscopic resection for synchronous early colon cancer ( defined as carcinoma limited to the mucosa or submucosa ) after sems placement is still unknown . if a synchronous early colorectal cancer is resected preoperatively using the endoscopic technique , we can evaluate its pathologic findings precisely and assess the possibility of curatively treating the lesion .
after successful placement of the sems , we performed a scheduled second total colonoscopy and detected 3 synchronous early cancers in the ascending and descending colons and the rectum , respectively ( fig .  1 ) .
for the ascending colon cancer , which was a protruding 30-mm lesion ( type 0-is 8) , we attempted endoscopic submucosal dissection ( esd ) ; however , we failed to complete the procedure because of severe fibrosis in the submucosal layer .
sems placement in the sigmoid colon ( orange square ) . in this case , melanosis coli was found in the colon .
we could not accomplish esd in the ascending colon cancer because of severe fibrosis in the submucosal layer .
however , we curatively resected the descending colon cancer with esd ( blue square ) and the rectal cancer with emr ( green square ) .
the descending colon cancer was a flat elevated 30-mm lesion ( type 0-iia ) and the rectal cancer was a protruding 10-mm lesion ( type 0-is ) , for which we successfully performed esd and endoscopic mucosal resection ( emr ) , respectively .
the histologic findings were that both lesions were intramucosal carcinoma ( ptis ) and the margins were free of carcinoma cells .
therefore , we concluded that the descending colon cancer and the rectal cancer could only be curatively treated via endoscopic resection .
our findings indicated the need to perform right hemicolectomy and sigmoidectomy ( pt3 , pn1 , cm0 ) .
histologic findings for the ascending colon revealed that the lesion was intramucosal carcinoma ( ptis ) with severe fibrosis in the submucosal layer .  
after successful placement of the sems , we performed a scheduled second total colonoscopy and detected a synchronous early cancer in the transverse colon ( fig .  2 ) .
this mass was undetectable during stent placement because neither colonic preparation with polyethylene glycol nor precise screening for synchronous lesions was possible owing to the emergent obstruction .  

we curatively resected the adenoma in the ascending colon ( red square ) and the early colon cancer in the transverse colon ( blue square ) with emr . for the transverse colon cancer , a flat elevated lesion with a slight depression and a diameter of 15  mm ( type 0-iia  +  iic ) , we successfully performed esd .
the histologic findings revealed that the lesion included well - differentiated adenocarcinoma cells that had invaded the submucosal layer ( pt1b , sm 2200 m ) .
although the margins were free of carcinoma cells , we concluded that surgery was necessary .
we performed an expanded right hemicolectomy ( pt4 , pn2 , pm1[h1 ] ) , including the esd scar .
after successful placement of the sems , we performed a scheduled second total colonoscopy and detected 2 synchronous tumors : 1 in the ascending and 1 in the transverse colon ( fig . 
3 ) . for the ascending tumor , which was a 15-mm flat elevated lesion ( type 0-iia ) , we performed emr and pathologically found that the lesion type was tubular adenoma . for the transverse colon cancer , which was a 20-mm flat elevated lesion ( type 0-iia )
the histologic findings revealed that the lesion type was intramucosal carcinoma ( ptis ) and the margins were free of carcinoma cells .
our results indicated the need to perform a low anterior resection ( pt4 , pn1 , cm1 ) .  

we curatively treated the early colon cancer in the transverse colon with esd ( red square ) .
after successful placement of the sems , we performed a scheduled second total colonoscopy and detected 3 synchronous early cancers in the ascending and descending colons and the rectum , respectively ( fig .  1 ) .
for the ascending colon cancer , which was a protruding 30-mm lesion ( type 0-is 8) , we attempted endoscopic submucosal dissection ( esd ) ; however , we failed to complete the procedure because of severe fibrosis in the submucosal layer .
sems placement in the sigmoid colon ( orange square ) . in this case , melanosis coli was found in the colon .
we could not accomplish esd in the ascending colon cancer because of severe fibrosis in the submucosal layer .
however , we curatively resected the descending colon cancer with esd ( blue square ) and the rectal cancer with emr ( green square ) .
the descending colon cancer was a flat elevated 30-mm lesion ( type 0-iia ) and the rectal cancer was a protruding 10-mm lesion ( type 0-is ) , for which we successfully performed esd and endoscopic mucosal resection ( emr ) , respectively .
the histologic findings were that both lesions were intramucosal carcinoma ( ptis ) and the margins were free of carcinoma cells .
therefore , we concluded that the descending colon cancer and the rectal cancer could only be curatively treated via endoscopic resection .
our findings indicated the need to perform right hemicolectomy and sigmoidectomy ( pt3 , pn1 , cm0 ) .
histologic findings for the ascending colon revealed that the lesion was intramucosal carcinoma ( ptis ) with severe fibrosis in the submucosal layer .
after successful placement of the sems , we performed a scheduled second total colonoscopy and detected a synchronous early cancer in the transverse colon ( fig .  2 ) .
this mass was undetectable during stent placement because neither colonic preparation with polyethylene glycol nor precise screening for synchronous lesions was possible owing to the emergent obstruction .  

we curatively resected the adenoma in the ascending colon ( red square ) and the early colon cancer in the transverse colon ( blue square ) with emr . for the transverse colon cancer , a flat elevated lesion with a slight depression and a diameter of 15  mm ( type 0-iia  +  iic ) , we successfully performed esd .
the histologic findings revealed that the lesion included well - differentiated adenocarcinoma cells that had invaded the submucosal layer ( pt1b , sm 2200 m ) .
although the margins were free of carcinoma cells , we concluded that surgery was necessary .
we performed an expanded right hemicolectomy ( pt4 , pn2 , pm1[h1 ] ) , including the esd scar .
an 81-year - old man underwent sems for obstructive rectal cancer . after successful placement of the sems , we performed a scheduled second total colonoscopy and detected 2 synchronous tumors : 1 in the ascending and 1 in the transverse colon ( fig .  3 ) . for the ascending tumor , which was a 15-mm flat elevated lesion ( type 0-iia ) , we performed emr and pathologically found that the lesion type was tubular adenoma .
for the transverse colon cancer , which was a 20-mm flat elevated lesion ( type 0-iia ) , we successfully performed emr .
the histologic findings revealed that the lesion type was intramucosal carcinoma ( ptis ) and the margins were free of carcinoma cells .
our results indicated the need to perform a low anterior resection ( pt4 , pn1 , cm1 ) .  

we curatively treated the early colon cancer in the transverse colon with esd ( red square ) .
in recent years , complete colonoscopy after sems placement has been recognized as feasible 5 
 6 
 7 . however , the feasibility of endoscopic resection for synchronous early colon cancer after sems placement is still unknown . to date , few reports have described the use of endoscopic resection for synchronous early colon cancer after sems placement 5 
 7 .
reported a case involving early ascending colon cancer accompanied by obstructive sigmoid colon cancer 7 .
similarly , kim et al . reported a case involving early rectal cancer accompanied by obstructive advanced rectal cancer 5 , and they treated the early one , which was located in the distal side of the sems , with esd .
the 3 cases reported herein are similar to those described previously ; however , to the best of our knowledge , this is the first report to describe cases involving the treatment of synchronous early colon cancer with esd using a colonic stent .
we selected niti - s ( 22  mm or 18-mm diameter , 80-mm length , taewoong medical , south korea ) as our first line sems .   in our hospital , the average duration of sems placement before surgery was 56.4 days ( data not shown ) .
it has reported that surgery within 5 to 10 days is ideal for reducing stent - related complications . on the other hand
, we also believe that it is important to improve the patient s general condition and examine the patient s disease precisely before surgery .
in particular , in addition to cancer staging or checking cardiopulmonary functions , screening for synchronous colon cancers and endoscopic treatment of early synchronous cancers is essential before surgery .
, we have not observed any complications such as re - obstruction , bleeding , or perforation before surgery . for the second colonoscopy via sems , we selected a small - diameter colonoscope ( e.  g. , pcf - pq260  l , olympus medical , tokyo , japan ) .
we have performed colonoscopy through a sems for 12 patients so far and have detected synchronous cancers in 5 patients .  
we select a small - diameter colonoscope without any magnifying function for the second colonoscopy .
generally , it is possible to diagnose the characteristics of colonic neoplasms with white light endoscopy with indigo carmine dye with approximately 80  % accuracy .
pit patterns or narrow band imaging diagnosis using magnifying endoscopy is useful and provides a much higher confidence in the diagnosis .
a small - diameter colonoscope was selected for endoscopic resection ( e.  g. , pcf - q260ji or pcf - q260azi , olympus medical , tokyo , japan ) .
our results indicate that preoperative endoscopic treatment for synchronous early colon cancer after sems placement has a great advantage in that we can establish an appropriate surgical strategy for the patient .
endoscopic resection for synchronous early colon cancer enables identification of precise pathological information about a lesion compared with simple endoscopic observation . for cases in which lesions can be curatively treated with endoscopic resection
, we can shorten the length of colectomy and accomplish a single - stage surgical operation .
even if a lesion can not be resected using the endoscopic technique , we believe that surgical resection of the lesion is necessary and a multi - stage operation should be avoided .
other modalities , such as computed tomography colonography 9 and magnetic resonance - colonography 10 , have been reported to be effective for screening of the entire colon after sems placement .
although these minimally invasive modalities provide a high rate of discovery of synchronous lesions , scheduled second colonoscopies using stents have a great advantage in that they enable detection of lesions and biopsy or treatment of them with emr and esd .
the safety of total colonoscopy with sems has been reported in previous studies , which revelaed no major complications , such as massive bleeding or perforation 6 
 7 . in our cases and in previous cases 5 
 7
, there were no complications associated with the endoscopic treatment . because the number of cases is still inadequate ,
further investigations are needed to evaluate the safety of preoperative endoscopic treatment for synchronous early colorectal cancers after sems placement .
in conclusion , preoperative endoscopic resection combined with the esd technique for synchronous colorectal neoplasms after sems placement is thought to be effective as a surgical strategy for patients with malignant colorectal obstruction .
however , evaluation of more cases is necessary to assess the safety of these techniques .
 
 background and study aims : the feasibility of endoscopic resection for synchronous early colon cancer after placement of self - expandable metallic stents ( sems ) for malignant colorectal obstruction is unknown . 
 herein we evaluated 3 cases of endoscopic resection for synchronous early colorectal cancers after sems placement . 
 patient 1 was an 82-year - old man with obstructive sigmoid colon cancer . 
 we curatively treated the synchronous descending colon cancer with endoscopic submucosal dissection ( esd ) and the rectal cancer with endoscopic mucosal resection ( emr ) after sems placement . 
 this is the first reported case of a successful esd for synchronous early colon cancer via the use of a colonic stent . 
 patient 2 was an 81-year - old man with obstructive ascending colon cancer . 
 we resected the synchronous transverse colon cancer via esd . 
 histologic findings indicated that the carcinoma cells had invaded the submucosal layer . 
 therefore , we immediately performed expanded right - hemicolectomy . 
 patient 3 was an 81-year - old man with obstructive sigmoid colon cancer . 
 we curatively treated the synchronous transverse colon cancer with emr after sems placement . 
 there were no complications associated with the endoscopic treatments in any of the cases . 
 our results indicate that preoperative endoscopic resection combined with the esd technique for synchronous colorectal cancer after sems placement could be effective as a surgical strategy for patients with malignant colorectal obstruction . 
Introduction
Case Reports
Patient 1
Patient 2
Patient 3
Discussion
Conclusions