Endoscopic management of colorectal tumors less than 10 mm in size: Current status and future perspectives in Japan from a questionnaire survey

Q1: What is your indication for image-enhanced endoscopy with magnification for diminutive or small colorectal lesions?

Image-enhanced endoscopy (IEE), also known as virtual chromoendoscopy,4 has been developed for detailed diagnosis of GI lesions, as it enhances small vessels and structures on the surface of detected lesions in real-time. Furthermore, use of the magnification function can identify vessel and surface patterns resulting in an improvement of the diagnostic accuracy and confidence levels compared to that of non-magnification endoscopy.

Although IEE technology includes narrow-band imaging (NBI), i-scan, flexible spectral imaging color enhancement (FICE) or blue laser imaging (BLI), all participants had an NBI system and magnification colonoscope at their institutions. Of nine participants, six (64%) responded that ‘all detected lesions’ are candidates for IEE with magnification (Fig. 1). In contrast, three participants responded that they use it ‘depending on lesions’. These participants considered that IEE with magnification is not so essential when diagnosing lesions with typical findings in white light imaging (WLI). For example, sessile or pedunculated type, reddish, lobulation on the lesion surface for adenoma; or sessile type in the sigmoid colon and rectum; pale, mucous on the lesion surface for hyperplastic polyp.

Q2: What is your indication for chromoendoscopy without magnification for diminutive or small lesions?

Except for one participant, all responded that it ‘depends on lesions’ (Fig. 2). Targeted chromoendoscopy facilitates detection and characterization of particularly flat and depressed colorectal tumor which is associated with an increased risk of cancer. Depressed areas, loss of lobulation or expansion are significant findings for predicting deep submucosal invasive cancer regardless of lesion size. Such findings are enhanced after spraying indigocarmine dye.

As mentioned above, IEE with magnification can predict histology without any dyes. All participants agreed that chromoendoscopy is necessary to diagnose mucosal or submucosal lesions, but it is the next step after IEE with magnification.

Q3: What is your indication for chromoendoscopy with magnification (pit pattern diagnosis) for diminutive or small lesions?

Indigocarmine dye spraying or crystal violet or methylene blue staining is applied when enhancing superficial patterns. Kudo classification has been established for differentiating types of pit pattern: Type I, II, III, IV and V using a magnification endoscope for predicting lesion histology in the colon.5 Furthermore, Type V pit pattern is subclassified into V_I low-grade, V_I high-grade and V_N pit patterns. For distinction of neoplastic or non-neoplastic lesions, indigocarmine dye spraying is sufficient for most lesions, whereas crystal violet staining is more useful when identifying V_I subclassifications and it is required for estimating the depth of cancer invasion.

All participants responded that not all detected lesions are candidates for chromoendoscopy with magnification (Fig. 3). NBI with magnification has a high diagnostic accuracy rate for distinction of neoplastic or non-neoplastic lesions as well as pit pattern.6 For colorectal lesions less than 10 mm, clinical use of NBI with magnification is reasonable compared to that of pit pattern diagnosis. In contrast, diagnostic accuracy of NBI with magnification is not greater than that of pit pattern diagnosis for estimating the depth of cancer invasion. Although the prevalence of submucosal invasive cancers is actually very low (0.05% in diminutive polyps), pit pattern diagnosis should be attempted for making a treatment decision of whether to attempt endoscopic resection or surgery. Therefore, Japanese experts use NBI with magnification followed by pit pattern diagnosis by crystal violet staining and magnification when identifying the degree of dysplasia in adenomas or estimating depth of cancer invasion.

Q4: What do you usually use when removing diminutive polyps (<5 mm)?

Although we can remove diminutive polyps by cold polypectomy, there are two cold polypectomy procedures: cold snare polypectomy (CSP) and cold forceps polypectomy (CFP). Percentage of participants choosing CSP, CFP, hot snare polypectomy (HSP) and hot biopsy (HB) were 35%, 30%, 9% and 4%, respectively, when multiple answers were allowed (Fig. 4). When combining CSP and CFP as cold polypectomy, 65% of participants use cold polypectomy. All the participants who responded that they attempt CFP routinely use jumbo-type forceps which are designed for removing larger tissue samples.3 The frequency of choosing HB was low. According to the report of EFJ in 2013,7 22% of participants responded that they use HB for removing diminutive polyps. Comparing these results, the frequency of choosing HB for removing diminutive polyps seems to be decreasing. In contrast, based on the JPG, 13% chose no resection, even for adenoma.

Q5: What do you usually use when removing small polyps (6–9 mm)?

Percentage of using CSP, endoscopic mucosal resection (EMR) and HSP was 37%, 32% and 32%, respectively (Fig. 5). Multiple bite resection method using CFP is not recommended when removing polyps larger than 5 mm. HSP may be useful for low-grade adenoma because the duration of the procedure is shorter than for EMR. EMR is also carried out for high-grade adenoma, intramucosal cancer or slightly invasive cancers, because this procedure can remove more submucosal tissue for accurate histological evaluation of muscularis mucosa and submucosal layer compared with HSP.