Depressed Colorectal Lesions Research Articles

Efficacy of international web-based educational intervention in the detection of high-risk flat and depressed colorectal lesions higher (CATCH project) with a video: Randomized trial.

ObjectivesThree subcategories of high‐risk flat and depressed lesions (FDLs), laterally spreading tumors non‐granular type (LST‐NG), depressed lesions, and large sessile serrated lesions (SSLs), are highly attributable to post‐colonoscopy colorectal cancer (CRC). Efficient and organized educational programs on detecting high‐risk FDLs are lacking. We aimed to explore whether a web‐based educational intervention with training on FIND clues (fold deformation, intensive stool/mucus attachment, no vessel visibility, and demarcated reddish area) may improve the ability to detect high‐risk FDLs.MethodsThis was an international web‐based randomized control trial that enrolled non‐expert endoscopists in 13 Asian countries. The participants were randomized into either education or non‐education group. All participants took the pre‐test and post‐test to read 60 endoscopic images (40 high‐risk FDLs, five polypoid, 15 no lesions) and answered whether there was a lesion. Only the education group received a self‐education program (video and training questions and answers) between the tests. The primary outcome was a detection rate of high‐risk FDLs.ResultsIn total, 284 participants were randomized. After excluding non‐responders, the final data analyses were based on 139 participants in the education group and 130 in the non‐education group. The detection rate of high‐risk FDLs in the education group significantly improved by 14.7% (66.6–81.3%) compared with −0.8% (70.8–70.0%) in the non‐education group. Similarly, the detection rate of LST‐NG, depressed lesions, and large SSLs significantly increased only in the education group by 12.7%, 12.0%, and 21.6%, respectively.ConclusionShort self‐education focusing on detecting high‐risk FDLs was effective for Asian non‐expert endoscopists. (UMIN000042348).

Visual assessment of colorectal flat and depressed lesions by using narrow band imaging.

Background and study aims Visual assessment of laterally spreading tumors non-granular type (LST-NG) and depressed lesions by narrow band imaging (NBI) without magnification has not been studied. We investigated the role of non-magnifying NBI in detecting LST-NG and type IIc lesions on colonoscopy. Patients and methods This retrospective study examined consecutive patients diagnosed as having LST-NG and/or type IIc lesions in our hospital between August 2011 and July 2013. These lesions were classified as “Brownish area (BA),” “Brown only in the margins (O-ring sign),” “Same color as the normal mucosa (SC),” and “Whitish area (WA)” based on their appearance on non-magnifying NBI, and their appearance were compared with their histopathological findings. Results A total of 18 type IIc and 180 LST-NG lesions were analyzed. Among the type IIc lesions, 5 (28 %), 12 (67 %), and 1 (5 %) were classified as BA, O-ring sign, and SC, respectively. Among the LST-NG lesions, 126 (70 %), 26 (14 %), and 28 lesions (16 %) were classified as BA, O-ring sign, and SC, respectively. The IIc lesions were found to have 1 lesion (20 %) with high-grade dysplasia (HGD) in the BA, and 2 lesions (17 %) with invasive cancer (IC) in the O-ring sign group. Among the LST-NG lesions, 27 (21 %) were found to have IC and 49 (39 %), HGD in the BA group; 8 lesions (31 %) had IC and 4 (15 %) had HGD in the O-ring sign group; and 1 lesion (4 %) had IC and 4 (14 %) had HGD in the SC group. Conclusions Most flat and depressed colorectal lesions were seen on non-magnifying NBI as brown lesions with the exception of some flat lesions that were indistinguishable in color from the adjacent normal mucosa. Some of these flat lesions were also found to have HGD or IC.

Therapeutic endoscopy in the flat and depressed colorectal lesions after evaluation with flexible spectral imaging color enhancement and high-frequency endoscopic ultrasonography

Therapeutic endoscopy in the flat and depressed colorectal lesions after evaluation with flexible spectral imaging color enhancement and high-frequency endoscopic ultrasonography

PREVALENCE AND CLINICOPATHOLOGICAL FEATURES OF NONPOLYPOID COLORECTAL NEOPLASMS: SHOULD WE PAY MORE ATTENTION TO IDENTIFYING FLAT AND DEPRESSED LESIONS?

Flat and depressed (nonpolypoid) colorectal lesions have been described for over two decades by Japanese investigators. These neoplastic lesions are typically smaller than polypoid ones and can be more difficult to identify during screening colonoscopy. In particular, depressed type colorectal lesions are usually small in size, with a number of studies showing them to be at greater risk for developing high-grade dysplasia or submucosal invasive cancer. It has also been suggested that they may follow a different carcinogenic pathway to flat elevated or protruding adenomas. This paper summarizes recent data of nonpolypoid colorectal neoplasms from Western and Asian countries.

W1466: The Submucosal Invasive Rate of Depressed Type Colorectal Lesions Over the Past Decade

More than 20 years have passed since the 0-IIc lesion in the colorectum was first detected in 1985. Depressed type neoplasms are assumed to emerge directly from normal epithelium without going through a stage of adenomas, the “de novo” carcinogenesis. The aim of our study is to evaluate the clinical and pathological natures of small depressed type colorectal lesions according to the period.

Advanced Colon Polypectomy

Advanced Colon Polypectomy

Detectability of colorectal neoplastic lesions using a narrow‐band imaging system: A pilot study

Flat and depressed colorectal neoplastic lesions can be difficult to identify using conventional colonoscopy techniques. Narrow-band imaging (NBI) provides unique views especially of mucosal vascular network and helps in visualization of neoplasia by improving contrast. The aim of this study was to assess the feasibility of using NBI for colorectal neoplasia screening. Forty-seven consecutive patients, who underwent high definition colonoscopy (HDC) screening examinations revealing neoplastic lesions, were enrolled in our prospective study. No biopsies or resections were performed during the initial HDC, but patients in whom lesions were detected underwent further colonoscopies using NBI, with the results of the first examination blinded from the colonoscopist. They then received appropriate treatment. We compared diagnostic detection rates of neoplastic lesions for HDC and NBI procedures using total number of all identified neoplastic lesions as reference standard. Altogether, 153 lesions were detected and analyzed in 43 patients. Mean diagnostic extubation times were not significantly different (P = 0.18), but the total number of lesions detected by NBI was higher (134 vs 116; P = 0.02). Based on macroscopic type, flat lesions were identified more often by NBI (P = 0.04). As for lesion size, only flat lesions < 5 mm were detected more frequently (P = 0.046). Lesions in the right colon were identified more often by NBI (P = 0.02), but NBI missed two flat lesions >or= 10 mm located there. Narrow band imaging colonoscopy may represent a significant improvement in the detection of flat and diminutive lesions, but a future multi-center controlled trial should be conducted to fully evaluate efficacy for screening colonoscopies.

The Detection of Flat and Depressed Colorectal Lesions: Which Endoscopic Imaging Approach?

The secondary prevention of colorectal cancer (CRC) assumes that early detection and resection of precursor lesions disrupts the adenoma– carcinoma sequence and halts progression to invasive neoplastic disease. The adenoma– carcinoma sequence has until now formed the rationale for endoscopic therapies directed at reducing the incidence of CRC. The fact that snare polypectomy of exophytic lesions fails to prevent progression to carcinoma in up to 24% of cases has prompted reevaluation of the prevalence and clinicopathologic significance of flat and depressed colorectal lesions in Western population cohorts. Such lesions, although well-described in the Japanese literature, have only recently been reported in Western population cohorts. Debate has continued regarding their prevalence, anatomic localization, histopathologic characteristics, and proposed imaging modality of choice. Within this perspective, we summarize the key data pertinent to recently described endoscopic diagnostic modalities and detail their clinical applicability both for the detection of flat neoplastic lesions occurring in the “sporadic” patient cohort, familial polyposis syndromes, and chronic ulcerative colitis.

Short- and long-term outcomes of standardized EMR of nonpolypoid (flat and depressed) colorectal lesions ≥1 cm (with video)

Nonpolypoid (flat and depressed) colorectal lesions are increasingly recognized. Their endoscopic removal requires specialized EMR techniques, which are more complex to perform. Outcomes data on EMR of nonpolypoid neoplasms in the United States is needed. To determine the safety and efficacy of EMR in the resection of nonpolypoid colorectal neoplasms > or = 1 cm. Retrospective analysis. Veterans Affairs Palo Alto Health Care System. Over a 5-year period, patients who underwent EMR for nonpolypoid colorectal lesions > or = 1 cm. A standardized approach that included lesion assessment, classification, inject-and-cut EMR technique, reassessment, and treatment of residual tissue. Complete resection, bleeding, perforation, development of advanced cancer, and death. A total of 100 patients (125 lesions: 117 flat and 8 depressed) met inclusion criteria. Mean size was 16.7 +/- 7 mm (range, 10-50 mm). Histology included 5 submucosal invasive cancers, 5 carcinomas in situ, and 91 adenomas. Thirty-eight patients (48 lesions) did not receive surveillance colonoscopy: 8 had surgery, 16 had hyperplastic pathology, and 14 did not undergo repeat examination. Surveillance colonoscopy was performed on 62 patients (77 lesions). Complete resection was achieved in 100% of these patients after 1 to 3 surveillance colonoscopies. All patients received follow-up (mean [standard deviation] = 4.5 +/- 1.4 years); none developed colorectal cancer or metastasis. Single endoscopist, retrospective study. A standardized EMR (inject-and-cut) technique is a safe and curative treatment option in nonpolypoid colorectal neoplasms (> or = 1 cm) in the United States.

Detection and Treatment of Early Flat and Depressed Colorectal Cancer Using High-Magnification Chromoscopic Colonoscopy: A Change in Paradigm for Western Endoscopists?

Japanese researchers reported flat and depressed colorectal lesions in the 1980s. Such lesions were thought irrelevant to Western populations and described as "Phantom" or "Akitas" carcinoma. Many depressed neoplasms arise through the de novo pathogenic sequence and demonstrate early invasive characteristics. All investigators report difficulties in identifying flat and depressed lesions using conventional colonoscopy. Failure to detect and treat such lesions may be responsible for the current shortfalls in secondary colorectal cancer prevention. Given the introduction of colorectal cancer screening programs in the United Kingdom, Europe, and the United States, it is essential to re-evaluate the significance of flat lesions as applicable to Western cohorts and explore the safety and efficacy of new endoscopic technology and interventional therapeutics.

Novel clinical in vivo roles for indigo carmine: high-magnification chromoscopic colonoscopy

Since the adenoma–carcinoma sequence was first proposed by Morson in the 1970s, it has become widely accepted that detection and subsequent removal of polypoid adenomas from the colon reduces the incidence of colorectal cancer. These adenomas are relatively easy to detect by conventional colonoscopy; however, large population studies have shown that despite resection of polypoid adenomas, interval colorectal cancers still occurred. Recent advances in technology have given today's endoscopists access to high-resolution and high-magnification scopes, which has facilitated detection of flat and depressed colorectal lesions. Current data suggest that such morphologically distinct lesions may account for up to 30% of all colorectal adenomas. Furthermore, flat and depressed lesions of the large bowel may confer greater malignant potential compared to polypoid adenomas. The majority of flat lesions show only subtle changes by conventional colonoscopy, but the use of stains, such as indigocarmine, in addition to magnification colonoscopy can enhance their detection significantly. In this paper, we discuss the rationale for detecting flat colorectal lesions. We explore the use of high-magnification colonoscopy and chromoendoscopy, with particular reference to the application of indigocarmine, in this patient group. We also discuss the novel therapeutic techniques now available for these lesions.

Recent advances in chromoscopic colonoscopy and endomicroscopy

The basic rationale for secondary prevention of colorectal carcinoma is by endoscopic polypectomy. New technologies in the form of high-magnification or "zoom" colonoscopy complemented by chromoscopic agents permit early detection of neoplastic colorectal lesions, particularly flat and depressed types. Detailed morphologic characteristics of the surface crypt or "pit pattern" can be obtained with these techniques, enabling an in vivo "optical biopsy" and staging tool. Establishing suitability for endoscopic resection or surgical excision can be enhanced using these techniques. Furthermore, chromoscopic colonoscopy may have a role in routine endoscopic colorectal cancer surveillance programs in patients at high risk for colorectal neoplasia, such as those with long-standing ulcerative colitis and familial colorectal cancer syndromes. This review summarizes recent data regarding the prevalence and histopathologic characteristics of flat and depressed colorectal lesions in Western cohorts and describes how their detection and management can be improved by chromoscopy and magnification technology. We outline these techniques from a clinical perspective and describe the basic principles of endoscopic mucosal resection.

Predictive Value of Magnification Chromoendoscopy for Diagnosing Invasive Neoplasia in Nonpolypoid Colorectal Lesions and Stratifying Patients for Endoscopic Resection or Surgery

In nonpolypoid colorectal lesions, the presence of irregular, distorted glands in the colon (a disrupted crypt pattern) on magnification chromoendoscopy (MCE) is strongly associated with submucosal invasive cancer. The aim of the present study was to evaluate the ability of MCE to differentiate between an invasive crypt pattern and a noninvasive crypt pattern, including nonneoplastic lesions, and to assess the ability of this MCE classification to predict invasiveness and allow patients to be selected for endoscopic resection or surgical resection. In a prospective study including 1560 colonoscopies, 153 flat or depressed colorectal lesions were evaluated with MCE among 534 colorectal lesions; the remainder had a polypoid appearance. The pit pattern was classified as nonneoplastic (type II) or neoplastic (types III - V), and the latter was subdivided into noninvasive (types III or IV) or submucosally invasive (type V). Lesions with a nonneoplastic and noninvasive neoplastic appearance were resected endoscopically if technically feasible, whereas those with a type V pattern were resected surgically. The resection specimens were analyzed histologically in relation to the Vienna classification. Using this management strategy based on the pit pattern, 86 % (n = 70) of the type II lesions were hyperplastic; the remaining 11 had low-grade intraepithelial neoplasia. Type III and IV lesions (n = 58) represented either low-grade or high-grade intraepithelial neoplasia in 95 % of the cases. Three patients had sm1 (n = 2) or sm2/3 invasive cancers. Among the patients with type V lesions (n = 14), 11 had invasive cancers (four sm1 and seven sm2/3). Endoscopic differentiation based on the pit pattern thus had a positive predictive value (PPV) of 86 % and a negative predictive value of 96 % for distinguishing between nonneoplastic and neoplastic lesions. The pit pattern criteria for distinguishing between invasive and noninvasive neoplasia (including nonneoplastic lesions), and hence the choice between endoscopic and surgical resection, had a PPV of 79 % and a NPV of 98 %. Excluding nonneoplastic lesions, the NPV would be 95 %. The endoscopic pit pattern on MCE has only a moderate predictive value for nonneoplastic lesions, so that leaving these flat hyperplastic lesions in place on the basis of the endoscopic magnification appearance alone cannot be generally recommended. However, MCE has a good predictive value for guiding management toward either endoscopic resection (if technically feasible) or surgical resection.

Nonpolypoid (Flat and Depressed) Colorectal Neoplasms

Nonpolypoid (Flat and Depressed) Colorectal Neoplasms

USEFULNESS OF MULTI DETECTOR ROW COMPUTED TOMOGRAPHY FOR DETECTION OF FLAT AND DEPRESSED COLORECTAL CANCER

Background: Recently, the clinical usefulness of colorectal cancer screening by CT colonography has been reported in Europe and the USA. However, in Japan, the diagnosis of flat or depressed colorectal cancer lesions has been emphasized, and the question of whether CT colonography facilitates visualization of these lesions remains to be answered. In the present study, we compared the visualization of flat and depressed colorectal cancer lesions by CT colonography with that of protruding lesions.Methods: We investigated 33 Dukes A colorectal cancer lesions that had been examined by 3D‐CT, colonoscopy, and barium enema prior to surgery. In all patients, CT colonography was performed immediately after colonoscopy. Volume rendering was used for 3‐D rearrangement, and imaging findings were examined with respect to morphology, tumor diameter, and tumor height.Results: All (14/14) of the protruding‐type lesions were visualized by CT colonography, whereas 78.9% (15/19) of the flat and depressed‐type lesions were visualized. There was no significant difference in tumor diameter between protruding‐type lesions and flat and depressed‐type lesions. With respect to tumor height, 100% of the lesions measuring 2 mm or more in height were visualized, whereas only 42.9% of those measuring less than 2 mm in height were visualized; the difference was significant (P &lt; 0.001).Conclusions: These results suggest that the visualization capacity of CT colonography is associated with tumor height, but not with tumor diameter. Currently, lesions measuring 2 mm or more in height can be visualized reliably by CT colonography.

A prospective clinicopathological and endoscopic evaluation of flat and depressed colorectal lesions in the United Kingdom

Objectives Flat and depressed colorectal lesions are now reported in Western populations. The malignant potential, anatomical distribution, and other clinicopathological features have not been established in this group. This study aimed to assess prospectively the prevalence, clinicopathological, and endoscopic features of flat and depressed colorectal lesions in the United Kingdom. Methods A single endoscopist performed colonoscopy on 850 consecutive patients presenting for routine colonoscopy. All endoscopies were performed using a high magnification colonoscope with chromoscopy to facilitate detection of flat and depressed colorectal lesions. Results A total of 458 flat lesions were identified. Of these, 173 (38%) were hyperplastic and 285 (62%) adenomatous or beyond. Of the 173 hyperplastic flat lesions, 162 (94%) were located in the recto-sigmoid region. Of the 267 adenomas, 66 (25%) had areas of high grade dysplasia (HGD), with 54/66 (82%) being present in the right colon. Flat lesions <8 mm in diameter was more likely to contain HGD than those <8 mm ( p < 0.001). Nine of the 10 (90%) flat invasive adenoacarcinomas were in the right colon and all had a depressed morphological component. In contrast, HGD was observed in 58/466 (12%) of protuberant (sessile/pedunculated) adenomas of which 95% (55/58) were located in the left colon. In addition, HGD was present in 17% of all sessile adenomas versus 44.6% of flat lesions >8 mm in diameter ( p = 0.001). Of the 14 protuberant carcinomas, 13/14 (93%) were in the left colon. Synchronous lesions were found in 96/816 (12%) of cases. Of the 816 patients with two or more left-sided protuberant adenomas <8 mm (with or without HGD), 89 (11%) had one or more flat lesions in the right colon with HGD. Conclusions Flat adenomas and carcinomas have a high malignant potential compared to protuberant lesions and have a propensity for developing in the right hemi-colon. Total colonoscopy is required to detect such lesions, as only 18% of flat lesions would be in reach of the flexible sigmoidoscope.

The role of flat and depressed colorectal lesions in colorectal carcinogenesis: new insights from clinicopathological findings in high-magnification chromoscopic colonoscopy.

High-magnification chromoscopic endoscopy is a new technique which has been recently introduced to the UK. This technology, initially pioneered by the Japanese in the 1980s, has changed our understanding of the pathogenesis of colorectal cancer and our subsequent therapeutic strategies aimed at the secondary prevention of cancer. Magnification colonoscopic techniques when combined with colonic chromoscopy (dye spraying of the colon) permit in vivo assessments of lesions at a magnification and resolution similar to a stereomicroscope. Furthermore, flat/depressed adenomas and cancers can be diagnosed with increasing frequency and new resection practices performed. This technique is known as endoscopic mucosal resection. As gastrointestinal endoscopists adopt these new techniques, close liaison with histopathologists is essential to provide the highest standards of diagnostic accuracy. The histopathologist also needs to be aware of the endoscopic findings when interpreting specimens and hence must understand new endoscopic terminologies and classification systems that accompany the introduction of new technologies and therapeutic techniques. This article describes the controversies relating to the flat and depressed colorectal lesion, where these new endoscopic technologies are ideally suited. It then provides a working description of high-magnification chromoscopic colonoscopy including the Japanese 'pit pattern' and morphological classification system-information which will be provided to histopathologists with specimens obtained by these new techniques. Finally, we describe the procedure of endoscopic mucosal resection, as the type and quality of specimens received for histopathological analysis will be highly influenced by these techniques.

Molecular analysis of diminutive, flat, depressed colorectal lesions: Are they precursors of polypoid adenoma or early stage carcinoma?

Background: The diminutive, flat depressed colorectal lesion is a possible precursor of early stage carcinoma. However, the significance of this lesion in colon carcinogenesis remains unclear. Methods: Eighty-one diminutive flat lesions (<5 mm diameter) with a central depression (DPdep) were resected colonoscopically and their molecular characteristics were investigated. In parallel, 68 diminutive polyps (<5 mm diameter) with a polypoid growth pattern but no depression (DPpo) were analyzed as controls. After histopathologic diagnosis, only neoplastic tissues were stained by immunohistochemistry for p53 gene and cyclooxygenase 2 (COX-2) and the proliferation marker, Ki-67. Mutation of the K- ras gene was analyzed with the polymerase chain reaction-restriction fragment length polymorphism method by using DNA from microdissected tissue in paraffin sections. Results: Seventy-nine of 81 DPdep and 35 of 68 DPpo were diagnosed as neoplastic. Mild, moderate, and severe dysplasia were found in, respectively, 56, 15, and 8 DPdep polyps, and in 34, 1, and 0 DPpo polyps. Thus, DPdep were more likely to be neoplastic and to exhibit moderate and severe dysplasia compared with DPpo ( p < 0.0001). No DPdep or DPpo was positive for the p53 protein. The proportion of specimens with K- ras codon 12 mutation was 13.4% in diminutive polyps (DP), and tended to be lower in DPdep (8.6%) than in DPpo (25.0%) ( p = 0.073). The median (interquartile range) of the Ki-67 index of DPdep tended to be lower than that of DPpo (respectively, 0.0 [0.0-5.9] vs. 4.5 [0.0-17.1]; p = 0.0281). COX-2 overexpression was observed in 12 of 77 (15.6%) DP and there was no significant difference between DPdep (3 of 23, 13.0%) and DPpo (9 of 54, 16.7%). Conclusion: Diminutive, flat, depressed lesions in this study had low rates of the genetic alterations associated with malignant progression. This indicates that either a different neoplastic mechanism is operative or that these lesions have a lower malignant potential than indicated by their histopathologic features. (Gastrointest Endosc 2002;56:663-71.)

Molecular analysis of diminutive, flat, depressed colorectal lesions: are they precursors of polypoid adenoma or early stage carcinoma?

The diminutive, flat depressed colorectal lesion is a possible precursor of early stage carcinoma. However, the significance of this lesion in colon carcinogenesis remains unclear. Eighty-one diminutive flat lesions (<5 mm diameter) with a central depression (DPdep) were resected colonoscopically and their molecular characteristics were investigated. In parallel, 68 diminutive polyps (<5 mm diameter) with a polypoid growth pattern but no depression (DPpo) were analyzed as controls. After histopathologic diagnosis, only neoplastic tissues were stained by immunohistochemistry for p53 gene and cyclooxygenase 2 (COX-2) and the proliferation marker, Ki-67. Mutation of the K-ras gene was analyzed with the polymerase chain reaction-restriction fragment length polymorphism method by using DNA from microdissected tissue in paraffin sections. Seventy-nine of 81 DPdep and 35 of 68 DPpo were diagnosed as neoplastic. Mild, moderate, and severe dysplasia were found in, respectively, 56, 15, and 8 DPdep polyps, and in 34, 1, and 0 DPpo polyps. Thus, DPdep were more likely to be neoplastic and to exhibit moderate and severe dysplasia compared with DPpo (p < 0.0001). No DPdep or DPpo was positive for the p53 protein. The proportion of specimens with K-ras codon 12 mutation was 13.4% in diminutive polyps (DP), and tended to be lower in DPdep (8.6%) than in DPpo (25.0%) (p = 0.073). The median (interquartile range) of the Ki-67 index of DPdep tended to be lower than that of DPpo (respectively, 0.0 [0.0-5.9] vs. 4.5 [0.0-17.1]; p = 0.0281). COX-2 overexpression was observed in 12 of 77 (15.6%) DP and there was no significant difference between DPdep (3 of 23, 13.0%) and DPpo (9 of 54, 16.7%). Diminutive, flat, depressed lesions in this study had low rates of the genetic alterations associated with malignant progression. This indicates that either a different neoplastic mechanism is operative or that these lesions have a lower malignant potential than indicated by their histopathologic features.

EVALUATION OF THE COLOR‐EMPHASIS SYSTEM AS AN ENDOSCOPIC DIAGNOSTIC METHOD: IS THE ADOPTED TYPE HEMOGLOBIN INDEX COLOR EMPHASIS USEFUL FOR THE DIAGNOSIS OF SUPERFICIAL TYPE COLON TUMORS?

The difficulty in an endoscopic diagnosis of colorectal tumors depends mainly on their gross configuration. As the superficial flat type and depressed type tumors are usually detected endoscopically by a faint redness on their surface, we evaluated the usefulness of an adopted type hemoglobin index color emphasis system in the lesion of a non‐granular (NG) type laterally spreading tumor (LST). The NG‐type LST was composed of only a flat surface without any nodules. The frequency of Tis was 20.2% and that of T1/T2 was 15.7% in the lesion of the NG‐type LST. Results showed that the adopted type hemoglobin index color emphasis system can emphasize the color level, as the redness and whiteness intensified in this system. The degree of redness and whiteness depended on the emphasis level, and the clarity of colors became clearer in level 5 than level 3 in a lesion of the NG‐type LST. This system may thus contribute to the endoscopic diagnosis of flat and depressed type colorectal lesions.