squamous cell carcinoma ( scc ) of the anal canal is a relatively rare malignancy , accounting for only approximately 2% of all gastrointestinal carcinomas .
the 5-year survival of patients with scc of the anal canal has been reported as 58% .
there are some reports regarding the potential prognostic factors of this tumor . similar to other malignant tumors , disease progression has been demonstrated to represent one of the major adverse prognostic factors for scc of the anal canal .
previously , abdominoperineal resection was the most commonly used treatment procedure for this malignancy ; however , scc has a good sensitivity to chemoradiotherapy and , for this reason , it has become the standard treatment strategy for scc of the anal canal [ 4 , 5 ] . on the other hand
, there are currently very few reports of early scc of the anal canal resected by endoscopic submucosal dissection ( esd ) . herein , we present 2 rare cases of early scc of the anal canal resected using this approach .
a white , flat , elevated lesion , 15 mm in size , was identified from the rectum to the dentate line of the anal canal on internal hemorrhoids ( fig .
magnifying endoscopy with narrow - band imaging ( nbi ) showed irregular vascular patterns ( dilatation , tortuous running , caliber changes , and different shapes ) ( fig .
1b ) . a chromoendoscopy with indigo - carmine dye showed the edge of the lesion clearly ; it revealed a lobulated , flat , and elevated lesion ( fig .
endoscopically , it was diagnosed as an early scc of the anal canal ( carcinoma in situ ) .
both the vertical and horizontal cut ends of the tumor were negative . in the superficial layer , koilocytosis , a change of cytoplasms with vacuoles , was recognized ( fig .
an immunohistochemical evaluation showed strong expressions of p53 , ki-67 , and p16 , indicating that the patient was likely infected with the human papillomavirus ( hpv ) ( fig .
the histopathological diagnosis was scc in situ without vessel invasion . at the latest follow - up ( 12 months after esd ) ,
she underwent a colonoscopy , and a white , papillary , flat , elevated lesion , 25 mm in size , was identified from the dentate line to the anal canal ( fig .
2a ) . a magnifying endoscopy with nbi showed irregular vascular patterns ( dilatation , tortuous running , caliber changes , and different shapes ) ( fig
chromoendoscopy with indigo - carmine dye showed the edge of the lesion clearly and revealed a lobulated , elevated lesion .
in addition , this lesion was clearly visible inside the dentate line ( fig . 2c ) and easily identified by chromoendoscopy with iodine staining ( fig .
the lesion was resected en bloc with the entire circumference of the rectum lumen ( fig .
an immunohistochemical evaluation showed strong expressions of p53 , ki-67 , and p16 ( fig .
a white , flat , elevated lesion , 15 mm in size , was identified from the rectum to the dentate line of the anal canal on internal hemorrhoids ( fig .
magnifying endoscopy with narrow - band imaging ( nbi ) showed irregular vascular patterns ( dilatation , tortuous running , caliber changes , and different shapes ) ( fig .
1b ) . a chromoendoscopy with indigo - carmine dye showed the edge of the lesion clearly ; it revealed a lobulated , flat , and elevated lesion ( fig .
endoscopically , it was diagnosed as an early scc of the anal canal ( carcinoma in situ ) .
both the vertical and horizontal cut ends of the tumor were negative . in the superficial layer , koilocytosis , a change of cytoplasms with vacuoles , was recognized ( fig .
an immunohistochemical evaluation showed strong expressions of p53 , ki-67 , and p16 , indicating that the patient was likely infected with the human papillomavirus ( hpv ) ( fig .
the histopathological diagnosis was scc in situ without vessel invasion . at the latest follow - up ( 12 months after esd ) ,
she underwent a colonoscopy , and a white , papillary , flat , elevated lesion , 25 mm in size , was identified from the dentate line to the anal canal ( fig .
2a ) . a magnifying endoscopy with nbi showed irregular vascular patterns ( dilatation , tortuous running , caliber changes , and different shapes ) ( fig
chromoendoscopy with indigo - carmine dye showed the edge of the lesion clearly and revealed a lobulated , elevated lesion .
in addition , this lesion was clearly visible inside the dentate line ( fig . 2c ) and easily identified by chromoendoscopy with iodine staining ( fig .
the lesion was resected en bloc with the entire circumference of the rectum lumen ( fig .
the histopathological diagnosis was scc in situ without vessel invasion . in the superficial layer , koilocytosis
an immunohistochemical evaluation showed strong expressions of p53 , ki-67 , and p16 ( fig .
it is strongly associated with hpv infection , which is the causative agent in approximately 8085% of all patients . anal intercourse and a high lifetime number of sexual partners
increase the risk of persistent hpv infection in both men and women , which in turn may eventually lead to malignancy . among more than 130 different hpv subtypes
, hpv16 is the most prevalent in anal carcinoma and is present in up to 89% of all hpv - positive anal carcinoma patients [ 7 , 8 , 9 ] .
increased p16 expression is a well - established surrogate marker for tumors with transcriptional active hpv .
moreover , a long - recognized pathognomonic feature of hpv infection is the appearance of halo or koilocytotic cells in the differentiated layers of the squamous epithelium .
these koilocytes are squamous epithelial cells that contain an acentric , hyperchromatic nucleus that is displaced by a large perinuclear vacuole . for detecting early scc of the anal canal , the use of magnifying endoscopy with nbi and indigo - carmine dye spraying has been previously reported .
nbi is a novel noninvasive optical technique that uses reflected light to visualize the organ surface and it can be used to qualitatively diagnose and differentiate between neoplastic and nonneoplastic esophageal lesions .
many studies have demonstrated the usefulness of nbi findings by discovering brownish dots [ dilated intraepithelial papillary capillary loops ( ipcls ) ] , tortuous ipcls , caliber changes in ipcls , a variety in ipcl shapes , demarcation lines , and brownish epithelium in the diagnosis of squamous mucosal high - grade neoplasia .
similarly to esophageal neoplasia , scc of the anal canal also consists of malignant squamous cells .
therefore , it is considered possible to qualitatively diagnose scc of the anal canal using nbi .
colorectal esd has become a standard therapy for large early colorectal carcinomas in japan , largely owing to the fact that it can be used to resect most types of lesions , regardless of their size or location . however , colorectal esd is more technically demanding than esophageal and gastric esd , as the anatomic features of the large intestine , which is a long luminal organ with many folds and flexures , hinder the manipulation of the endoscope for some lesions , and due to the fact that the intestinal wall is thin and easy to perforate .
there have been some reports indicating that the establishment of a systematic training program for the technically more difficult colorectal esd , in addition to the further development and refinement of esd - related instruments , devices , equipment , and injection solutions , may help facilitate the increased use of colorectal esd throughout the world [ 14 , 15 ] .
we have previously reported on the clinical usefulness of esd for lesions close to the dentate line , which should be performed with the following considerations in mind : ( 1 ) local anesthesia to prevent anal pain should be administered before submucosal injection of hyaluronic acid ; ( 2 ) a shallow peripheral mucosal incision should be made to prevent bleeding , and ( 3 ) the blood vessels should be appropriately handled using hemostatic forceps . as demonstrated in the present study , even in cases of anal canal tumors , we could perform esd successfully using this procedure . in the future , as the clinicopathologic characteristics and prognosis of early scc of the anal canal are currently not clear , further studies are needed in order to reveal the indications of esd for early scc of the anal canal .
 the standard treatment approach for squamous cell carcinoma ( scc ) of the anal canal includes abdominoperineal resection and chemoradiotherapy . however , there are currently very few reports of early scc of the anal canal resected by endoscopic submucosal dissection ( esd ) . 
 we report 2 rare cases of scc of the anal canal resected by esd . in case 1 , 
 a 66-year - old woman underwent a colonoscopy due to blood in her stool , and an elevated lesion , 15 mm in size , was identified from the rectum to the dentate line of the anal canal on internal hemorrhoids . 
 the lesion was diagnosed as an early scc of the anal canal , and esd was successfully performed . 
 the histopathological diagnosis was scc in situ . in case 2 , 
 a 71-year - old woman underwent a colonoscopy due to constipation , and an elevated lesion , 25 mm in size , was identified from the dentate line to the anal canal . 
 the lesion was diagnosed as early - stage scc of the anal canal , and esd was successfully performed . 
 the histopathological diagnosis was scc in situ . 
 no complications or recurrence after esd occurred in either case . 
Introduction
Case Reports
Case 1
Case 2
Discussion
Disclosure Statement