**3. New problems caused by accurate colonoscopy and the key to a solution to these problems**

It has here been reported that a combination of AFI and a TH detects more colorectal neoplasms than does conventional WLI colonoscopy, however most of the lesions detected in the trial were small, low-grade adenomas. Although detection and resection of colorectal adenomas is an efficacious and basic strategy for prevention of colorectal cancer, such an accurate diagnostic method for detection of colorectal neoplasms increases the cost, time and labor required for formal histopathological diagnosis of the resected small indolent neoplasms. Because it results in a high yield of colorectal neoplasms, more accurate colonoscopy can, in itself, cause a new problem.

The 'DISCARD' (Detect InSpect ChAracterize Resect and Discard) policy (Ignjatovic et al., 2009), which is supported by 'optical diagnosis' using NBI without magnification, can lead to substantial savings in cost, time and labor for formal histopathology, making it a really impressive proposal. In the 'DISCARD' trial, it was reported that the capability to correctly diagnose polyps during screening colonoscopy (optical diagnosis) allows recto-sigmoid hyperplastic polyps to be left *in situ* and small adenomas to be resected and discarded without the need for formal histopathology. This policy could be key to a solution to the new problems created by the high yields of the new colonoscopic techniques.

However, small polypoid invasive cancer, though uncommon, does actually exist. The present authors have detected an 8 mm polypoid carcinoma that had invaded the submucosa in the sigmoid colon (Fig. 8). It looked like a small adenoma in the sigmoid colon.

We suppose that NBI without magnification cannot distinguish a small polypoid invasive cancer from a small indolent adenoma because their shapes are so similar. Although invasive cancer requires colorectomy with lymph node dissection after estimation of the possibility of lymph node metastasis, such lesions may be discarded without formal histopathology under the 'DISCARD' policy. Furthermore, NBI without magnification does not allow assessment of the degree of dysplasia. In the United States, the interval between surveillance colonoscopies is determined according not only to the number of detected adenomas and their size, but also to the degree of dysplasia and the presence of villous components. Therefore, the 'DISCARD' policy cannot be adopted in countries supporting the US guidelines. An alternative endoscopic technique is proposed here, one that, while decreasing the number of formal histopathological examinations required, is expected to provide information about the histopathological dysplasia of any lesions detected.

The primary endpoint, neoplasm detection rate (number of detected neoplasms per patient [95% CI]) in the AFI + TH group was significantly higher than in the WLI alone group (1.96 [1.50–2.43] vs 1.19 [0.93–1.44], *P* = 0.023 [Tukey-Kramer multiple comparison method]). AFI with a TH detected more neoplasms than did conventional colonoscopy (Fig. 7). Subgroup analysis revealed that mounting a TH resulted in a higher detection rate for polypoid neoplasms than did not mounting a TH, and that AFI observation resulted in a higher detection rate for flat neoplasms than did WLI observation. It was concluded that a combination of the different complementary mechanisms of AFI and a TH would be

**3. New problems caused by accurate colonoscopy and the key to a solution** 

It has here been reported that a combination of AFI and a TH detects more colorectal neoplasms than does conventional WLI colonoscopy, however most of the lesions detected in the trial were small, low-grade adenomas. Although detection and resection of colorectal adenomas is an efficacious and basic strategy for prevention of colorectal cancer, such an accurate diagnostic method for detection of colorectal neoplasms increases the cost, time and labor required for formal histopathological diagnosis of the resected small indolent neoplasms. Because it results in a high yield of colorectal neoplasms, more accurate

The 'DISCARD' (Detect InSpect ChAracterize Resect and Discard) policy (Ignjatovic et al., 2009), which is supported by 'optical diagnosis' using NBI without magnification, can lead to substantial savings in cost, time and labor for formal histopathology, making it a really impressive proposal. In the 'DISCARD' trial, it was reported that the capability to correctly diagnose polyps during screening colonoscopy (optical diagnosis) allows recto-sigmoid hyperplastic polyps to be left *in situ* and small adenomas to be resected and discarded without the need for formal histopathology. This policy could be key to a solution to the

However, small polypoid invasive cancer, though uncommon, does actually exist. The present authors have detected an 8 mm polypoid carcinoma that had invaded the submucosa in the sigmoid colon (Fig. 8). It looked like a small adenoma in the sigmoid

We suppose that NBI without magnification cannot distinguish a small polypoid invasive cancer from a small indolent adenoma because their shapes are so similar. Although invasive cancer requires colorectomy with lymph node dissection after estimation of the possibility of lymph node metastasis, such lesions may be discarded without formal histopathology under the 'DISCARD' policy. Furthermore, NBI without magnification does not allow assessment of the degree of dysplasia. In the United States, the interval between surveillance colonoscopies is determined according not only to the number of detected adenomas and their size, but also to the degree of dysplasia and the presence of villous components. Therefore, the 'DISCARD' policy cannot be adopted in countries supporting the US guidelines. An alternative endoscopic technique is proposed here, one that, while decreasing the number of formal histopathological examinations required, is expected to provide information about the histopathological dysplasia of any lesions

new problems created by the high yields of the new colonoscopic techniques.

efficacious in the detection of colorectal neoplasms.

colonoscopy can, in itself, cause a new problem.

**to these problems** 

colon.

detected.

Fig. 8. Small (8 mm) submucosally invasive, polypoid colon cancer. (A) Endoscopic image of a small polypoid (Paris classification, 0-Is) lesion in the sigmoid colon. (B) Microscopic image of endoscopically resected specimen (hematoxylin and eosin stain). The lesion has invaded the submucosal layer. (C) Microscopic image of endoscopically resected specimen (Desmin stain). The muscularis mucosa has been disrupted by the invading carcinoma
