Efficacy of additional tissue sections for diminutive colorectal adenomas pathologically diagnosed as normal mucosa: a retrospective, cross-sectional study in Japan

Tsuyoshi Ishii; Toshihiro Nishizawa; Hidenobu Watanabe; Masaya Sano; Ai Fujimoto; Yoshiyuki Takahashi; Ryo Shimizu; Hirotoshi Ebinuma; Takahisa Matsuda; Osamu Toyoshima

doi:10.5946/ce.2024.265

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Original Article Efficacy of additional tissue sections for diminutive colorectal adenomas pathologically diagnosed as normal mucosa: a retrospective, cross-sectional study in Japan: Tsuyoshi Ishii^1,2,3, Toshihiro Nishizawa^1,4, Hidenobu Watanabe⁵, Masaya Sano^1,6, Ai Fujimoto^1,3, Yoshiyuki Takahashi¹, Ryo Shimizu^1,3, Hirotoshi Ebinuma⁴, Takahisa Matsuda³, Osamu Toyoshima¹; Clinical Endoscopy 2025;58(4):577-585.
DOI: https://doi.org/10.5946/ce.2024.265
Published online: July 7, 2025

¹Gastroenterology, Toyoshima Endoscopy Clinic, Tokyo, Japan

²Department of Gastroenterology, Toranomon Hospital, Tokyo, Japan

³Division of Gastroenterology and Hepatology, Department of Internal Medicine (Omori), School of Medicine, Toho University, Tokyo, Japan

⁴Department of Gastroenterology and Hepatology, International University of Health and Welfare, Narita Hospital, Narita, Japan

⁵Pathology and Cytology Laboratory Japan, Tokyo, Japan

⁶Division of Gastroenterology and Hepatology, Department of Internal Medicine, Tokai University School of Medicine, Isehara, Japan

Correspondence: Toshihiro Nishizawa Department of Gastroenterology and Hepatology, International University of Health and Welfare, Narita Hospital, 852 Hatakeda, Narita, Chiba, 286-8520, Japan E-mail: nisizawa@kf7.so-net.ne.jp

• Received: September 28, 2024 • Revised: December 23, 2024 • Accepted: January 10, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Abstract
Graphical abstract
INTRODUCTION
METHODS
RESULTS
DISCUSSION
NOTES
REFERENCES

Abstract

Background/Aims
Endoscopists occasionally encounter discrepancies between endoscopic and pathological diagnoses after colorectal polypectomies. This study aimed to evaluate the efficacy of additional sections for diagnostic discrepancies.
Methods
We examined polyps endoscopically diagnosed as adenomas or suspected adenomas that were resected and pathologically diagnosed as adenomas or normal mucosa. Adenomas pathologically diagnosed with initial sections were categorized as the “adenoma by initial section” group. Based on the re-diagnosis with additional sectioning, they were assigned to the “adenoma by additional section” or “normal mucosa by both sections” groups.
Results
In the initial pathological diagnosis of 993 lesions, 850 were diagnosed as adenomas and 143 as normal mucosa. Additional sections corrected the pathological diagnoses in 23.8% (34/143) of cases. The rate of high confidence was significantly higher in the “adenoma by additional section” group than in the “normal mucosa by both sections” group (64.7% vs. 38.5%, p<0.01). Lesions in the “adenoma by additional section” group were significantly smaller than those in the “adenoma by initial section” group (2.7 vs. 3.8 mm, p<0.05).
Conclusions
Diminutive adenomas can cause discrepancies between endoscopic and pathological diagnoses. Additional sections may help revise the pathological diagnoses, particularly for lesions with high confidence.
Keywords: Diagnosis; Endoscopy; Microtomy; Pathology

Graphical abstract

INTRODUCTION

The increasing incidence of colorectal cancer (CRC) is a global health concern,¹^,² and its prevention is important.³ Endoscopic resection of colorectal adenomas can reduce morbidity by 10% and prevent 47% of CRC-related deaths, based on the United States National Polyp Study.⁴^,⁵

In routine practice, 70% to 80% of colorectal polyps are diminutive.⁶ The incidence of carcinoma in diminutive colorectal lesions is rare, ranging from 0.03% to 0.3%.⁷^,⁸ Although there is still some debate as to whether diminutive adenomas should be removed, the American Gastroenterological Association and European Society of Gastrointestinal Endoscopy guidelines strongly recommend endoscopic resection of all detected adenomas, regardless of size.⁹^,¹⁰ With advancements in science and technology, the quality of endoscopic images has improved.¹¹^,¹² Consequently, the percentage of diminutive polyps detected using colonoscopy is increasing.¹³^,¹⁴ In clinical practice, opportunities for removing diminutive polyps are increasing. Even if adenomas are diminutive, the number of adenomas indicate the surveillance colonoscopy interval. The absence of adenomas or the presence of 1 to 2 adenomas indicates a low-risk group, and a follow-up colonoscopy after 5 to 10 years is recommended. However, a follow-up colonoscopy after 3 years is recommended for the high-risk group, which presents with any of the following: ≥3 adenomas, adenomas ≥10 mm, high-grade dysplasia, villous component, serrated lesions ≥10 mm, or atypical serrated lesions, in the guidelines by the Japan Gastroenterological Endoscopy Society.¹⁵

When lesions diagnosed as tumors are removed endoscopically, they are occasionally diagnosed as normal mucosa on pathological examination. Discrepancies between pathological and endoscopic diagnoses have been reported, particularly for diminutive polyps.¹⁶ These discrepancies may result from processing errors in pathology owing to their diminutive size. Additional sections (AS) of tissue may be effective for this error. Therefore, this study aimed to evaluate the efficacy of AS in such diagnostic discrepancies.

METHODS

Study overview

This retrospective cross-sectional study was conducted at a specialized outpatient endoscopy clinic in an urban area of Japan. The patients were enrolled between June 2023 and July 2023. This study included polyps diagnosed endoscopically as adenomas or suspected adenomas that were resected and pathologically diagnosed as adenomas or normal mucosa.

Endoscopic procedures

The endoscopy system EVIS X1 and CF-XZ1200, CF-HQ290Z, and PCF-H290Z colonoscopes (Olympus) were used in this study. Twenty endoscopists performed the colonoscopies. The median (interquartile range) adenoma detection rate was 41.2% (33.3%–51.0%) for the 20 endoscopists between January 2023 and December 2023. Chromoendoscopy using 0.01% indigo carmine with white-light imaging and/or texture and color enhancement imaging was utilized.¹⁷^-¹⁹ Cold snare polypectomy, cold forceps polypectomy, hot snare polypectomy, and endoscopic mucosal resection were performed appropriately. Cold forceps polypectomy was performed for polyps sized 1 to 4 mm, and cold snare polypectomy was performed for polyps sized 3–10 mm. In cases where cancer was suspected, endoscopic mucosal resection was performed. The reporting system used for endoscopic examinations was the T-file system (STS-Medic).²⁰

Colorectal polyps

The endoscopists described endoscopic findings such as the location, size, and endoscopic morphology of the polyps; the Japan Narrow Band Imaging Expert Team (JNET) classification; and the confidence level of endoscopic diagnosis for each polyp.¹⁹^,²¹^,²² The proximal colon was defined as the region extending from the cecum to the transverse colon. The size of the polyp was measured and compared with the thickness or width of the snare or forceps. Endoscopic morphology was evaluated based on the Paris classification²³ and the JNET classification.²⁴ The polyps were also assigned a high or low level of confidence in terms of predictive accuracy.²¹^,²⁵ High confidence in the diagnosis of adenoma was defined as follows²⁶^,²⁷: color was brown on narrow-band imaging (NBI), and in the surface pattern, the white structures were oval or tubular in shape and surrounded by brown vessels.²⁸ Low confidence was defined as lesions with the characteristics of both adenomas and serrated polyps. The characteristics of serrated polyps were as follows: their color was light, and on the surface pattern, white structures or pits were uniform and surrounded by lacy and thin vessels (some cases had no vessels). High confidence hypothetically indicated that the colonoscopist discarded the polyp without histological assessment, whereas low confidence indicated that the polyp was sent for histological analysis. Confidence was considered only during the polyp-level analysis.²² The histological evaluation was performed on both polyps with high and low confidence. Representative endoscopic images are shown in Figure 1.

Pathology

Pathological diagnoses were performed at the Pathology and Cytology Laboratory, Japan. Hematoxylin and eosin-stained tissue sections were analyzed by an experienced gastrointestinal pathologist (H.W.). Lesions diagnosed as adenomas in the initial pathological analysis were categorized into the “adenoma by initial section” group. Lesions diagnosed as normal mucosa in the initial pathological analysis were categorized into the “normal mucosa by initial section” group. For the “normal mucosa by initial section” group, AS were obtained and re-diagnosed. Based on the re-diagnosis, they were assigned to the “adenoma by additional section” or “normal mucosa by both sections” groups (Fig. 2). The microtome machine cut out a single 3-µm-thick section in the initial section. AS were obtained from the paraffin blocks, and three sections were cut.

Statistical analysis

All continuous variables in this study are expressed as mean±standard deviation or median with interquartile range. Welch’s t-test was used for continuous data to detect differences between groups. The chi-square test was used to compare the secondary outcomes by category. A p-value less than 0.05 was considered statistically significant. All analyses were conducted using the statistical software R ver. 4.2.2 (2022-10-31; R Foundation for Statistical Computing).

Ethics

This study complied with the Declaration of Helsinki and ethical guidelines for medical research in Japan. This study was approved by the Certified Institutional Review Board Ethics Committee of Yoyogi Mental Clinic (certificate number: RKK227). The study protocol was published on the clinic’s website (www.ichou.com), allowing patients to opt out of the study if desired. Written informed consent for the use of clinical information was obtained before colonoscopy.

RESULTS

Figure 2 presents a flowchart of the polyp enrollment. A total of 993 lesions that were endoscopically diagnosed as adenomas and resected were included in this study. In the initial pathological diagnoses, 850 and 143 lesions were diagnosed as adenomas and normal mucosa, respectively (Fig. 2). The characteristics of the “adenoma by initial section” and “normal mucosa by initial section” groups are shown in Table 1. Lesions in the “adenoma by initial section” group were significantly larger than those in the “normal mucosa by initial section” group (p<0.001). The rate of Paris type I lesions was significantly higher in the “adenoma by initial section” group than in the “normal mucosa by initial section” group (p<0.001). A significant difference was observed in the distribution of the JNET diagnoses between the “adenoma by initial section” and “normal mucosa by initial section” groups. The proportions of JNET type 1 in the “adenoma by initial section” and “normal mucosa by initial section” groups were 5.3% and 15.4%, respectively. The frequency of high confidence in the “adenoma by initial section” group was significantly higher than that in the “normal mucosa by initial section” group (p<0.001). The proportions of cold forceps polypectomy in the “adenoma by initial section” and “normal mucosa by initial section” groups were 38.7% and 71.3%, respectively.

For the “normal mucosa by initial section” group, AS were obtained and re-diagnosed. The “adenoma by additional section” and “normal mucosa by both sections” groups included 34 and 109 polyps, respectively. Table 2 compares the “adenoma by additional section” and “normal mucosa by both sections” groups. The high confidence rates were 64.7% and 38.5% in the “adenoma by additional section” and “normal mucosa by both sections” groups, respectively. The “adenoma by additional section” group was more likely to be diagnosed with high confidence than the “normal mucosa by both sections” group (p=0.007).

Table 3 compares the “adenoma by initial section” and “adenoma by additional section” groups. Lesions in the “adenoma by additional section” group tended to be located more often in the proximal colon compared with lesions in the “adenoma by initial section” group (p=0.038). Lesions in the “adenoma by additional section” group were smaller than those in the “adenoma by initial section” group (2.65 vs. 3.77 mm, p<0.001). A significant difference was observed in the distribution of the JNET diagnoses between the two groups. The proportions of JNET type 1 in the “adenoma by additional section” and “adenoma by initial section” groups were 20.6% and 5.3%, respectively. The high confidence rates were 85.5% and 64.7% in the “adenoma by initial section” and “adenoma by additional section” groups, respectively. The “adenoma by initial section” group was more frequently diagnosed with high confidence compared with the “adenoma by additional section” group (p<0.001).

DISCUSSION

Regarding the discrepancy between endoscopic and pathological diagnoses, AS corrected the pathological diagnosis in 23.8% (34/143) of cases, confirming that the endoscopic diagnosis was correct. This phenomenon is more likely to occur in small adenomas with high confidence in the endoscopic diagnosis. To the best of our knowledge, this study is the first to clarify the characteristics of lesions whose diagnosis was changed by AS after colorectal polypectomy.

There are several reports on the effect of AS on the discrepancy between endoscopic and pathological diagnoses after colorectal biopsies.²⁹^-³¹ The pathological diagnosis was revised based on AS in 10% to 31% of cases, indicating that pathological diagnosis using initial sections could fail to confirm an endoscopically suspected diagnosis. The revision rates in our study were similar, although the specimens were obtained after polypectomy and contained normal mucosa as resection margins. Wu et al.³⁰ reported that initial sections in cases of diagnosis revised by AS often contained lymphoid aggregates that mimicked small polyps. Lymphoid aggregates may cause failure of the initial sections.

Ponugoti et al.¹⁶ focused on endoscopic diagnoses for discrepancies between endoscopic and pathologic diagnoses and included 644 colorectal lesions that were ≤3 mm and diagnosed adenoma with high confidence. However, the pathological diagnosis was normal mucosa in 15.4% of 644 lesions. Two blinded external experts reviewed the endoscopic images. The adenomas and normal mucosa in the pathological diagnoses were endoscopically diagnosed as adenomas with high confidence in 96.9% and 93.9% of cases, respectively, by one expert and in 99.6% and 100% of cases, respectively, by another expert. Several factors, including pathological processing errors, may be responsible for this discrepancy. Tumors in the specimens must be captured and sectioned; however, failures are more likely in smaller lesions. The authors concluded that pathological diagnoses of polyps ≤3 mm in size are not the gold standard when endoscopic diagnoses are “adenoma” with high confidence and pathological diagnoses are “normal mucosa.” The results of our study support this conclusion.

Another factor contributing to this discrepancy is the limited accuracy of endoscopic diagnosis. A prospective multicenter study showed that the accuracy of endoscopic diagnosis for adenomas with high confidence was 91% for polyps 6 to 9 mm in size and 89% for polyps <5 mm in size.³² Endoscopic diagnosis for adenomas with high confidence is not always accurate. A previous study using a large-scale clinical practice database demonstrated the diagnostic accuracy of the JNET classification.²⁴ The diagnostic accuracy was stratified by size, and the accuracy of diagnosis for JNET type 1 was 98% for polyps sized ≥10 mm, 90% for those sized 6 to 9 mm, and 89% for those sized ≤5 mm. Rastogi et al.³³ also demonstrated that the accuracy of NBI in predicting adenoma decreases with decreasing polyp size. Although these previous studies showed a decline in the accuracy for diminutive lesions, this decline may be due to pathological processing errors in diminutive polyps. Pathological errors include challenges in capturing diminutive lesions during pathological processing. These errors may be caused by lymphoid aggregates mimicking small polyps. Considering the uncertainty of the pathology of diminutive polyps, endoscopic diagnosis of adenomas with high confidence may be considered the gold standard.

When the “adenoma by additional section” group was compared with the “adenoma by initial section” group, lesions in the “adenomas by additional section” group were significantly smaller, had a higher JNET type 1 rate, and tended to be distributed in the proximal colon. We previously reported unusual adenomas with a hyperplastic polyp appearance.³⁴^,³⁵ The lesions were diminutive and tended to develop in the proximal colon. Furthermore, unusual adenomas have different proliferative patterns, and the proliferative zone is confined to the lower two-thirds of the crypts, similar to hyperplastic polyps. The proliferative patterns of typical adenomas are confined to the upper third or are scattered along the entire axis of the crypt. Adenomas with lower proliferative zones are less common (2%); however, they are more likely to require AS because of their small size. Adenomas with lower proliferative zones may be one of the reasons for the high rates of JNET type 1 and its distribution in the proximal colon in the “adenoma by additional section group.”

There may be another reason why the “adenoma by additional section” group tended to be located more often in the proximal colon compared with the “adenoma by initial section” group. The European Society of Gastrointestinal Endoscopy recommends that all polyps should be resected except for diminutive polyps in the distal colorectum that are predicted with high confidence to be hyperplastic polyps.¹⁰ In our study, diminutive hyperplastic polyps in the distal colon were not resected according to several guidelines. In contrast, diminutive polyps in the proximal colon were resected when sessile serrated lesions or adenomas were suspected. This difference between the proximal and distal colons may have introduced bias.

This study had some limitations. First, this was a retrospective single-center study. However, the medical data recordings were well-controlled. Second, the timeframe and patient cohort were limited. Third, interobserver variability in confidence levels could exist, and our results should be validated in diverse settings for generalizability. Fourth, a cost analysis of AS was not performed. A detailed cost-effectiveness analysis should be conducted to assess the feasibility of routine use. The extra cost for AS was 1,500 ¥ (10 United States dollar) at the Pathology and Cytology Laboratory, Japan. Excessive AS in small lesions should be balanced with the clinical importance of the lesions.

In conclusion, diminutive adenomas can cause discrepancies between endoscopic and pathological diagnoses, and AS may help revise pathological diagnoses. The revision of the pathological diagnosis is likely in lesions with high confidence.

Conflicts of Interest

The authors have no potential conflicts of interest.

Funding

None.

Author Contributions

Conceptualization: OT; Data curation: MS; Formal analysis: TI, TN, OT; Investigation: MS, AF, YT, RS; Methodology: HW; Project administration: TN,OT; Resources: HE; Supervision: TM; Visualization: TN; Writing–original draft: TI, TN; Writing–review & editing: all authors.

Fig. 1.

Representative endoscopic images. An adenoma was detected using white-light imaging (A) and assigned a high level of confidence using narrow-band imaging (B). Another adenoma was detected using texture and color enhancement imaging (C) and was assigned a low level of confidence using narrow-band imaging (D).

Fig. 2.

Flowchart of polyp enrollment.

Table 1.

Patient and polyp characteristics

Characteristic	Total (n=993)	Normal mucosa by initial section group (n=143)	Adenoma by initial section group (n=850)	p-value
Age (yr)	60.9±10.9	59.7±10.8	61.0±10.9	0.21
Sex				0.11
Male	547 (55.1)	70 (49.0)	477 (56.1)
Female	446 (44.9)	73 (51.0)	373 (43.9)
Location				0.08
Proximal	658 (66.3)	104 (72.7)	554 (65.2)
Distal	335 (33.7)	39 (27.3)	296 (34.8)
Size (mm)	3.57±0.14	2.37±0.18	3.77±0.15	<0.001
Morphology^a)				<0.001
0–I	75 (7.6)	1 (0.7)	74 (8.7)
0–II	918 (92.4)	142 (99.3)	776 (91.3)
Japan Narrow Band Imaging Expert Team classification				<0.001
1	67 (6.7)	22 (15.4)	45 (5.3)
2A	908 (91.4)	121 (84.6)	787 (92.6)
2B	18 (1.8)	0 (0)	18 (2.1)
Confidence				<0.001
High	791 (79.7)	64 (44.8)	727 (85.5)
Low	202 (20.3)	79 (55.2)	123 (14.5)
Treatment				<0.001
Cold forceps polypectomy	431 (43.4)	102 (71.3)	329 (38.7)
Cold snare polypectomy	543 (54.7)	41 (28.7)	502 (59.1)
Endoscopic mucosal resection	19 (1.9)	0 (0)	19 (2.2)

Values are presented as mean±standard deviation or number (%).

^a)According to the Paris classification.

Table 2.

Comparison between the “adenoma by additional section” and “normal mucosa by both sections” groups

Characteristic	Adenoma by additional section group (n=34)	Normal mucosa by both sections group (n=109)	p-value
Age (yr)	63.2±9.6	58.6±10.9	0.06
Sex			0.59
Male	18 (52.9)	52 (47.7)
Female	16 (47.1)	57 (52.3)
Location			0.15
Proximal	28 (82.4)	76 (69.7)
Distal	6 (17.6)	33 (30.3)
Size (mm)	2.65±0.48	2.27±0.18	0.17
Morphology^a)			0.07
0–I	1 (2.9)	0 (0)
0–II	33 (97.1)	109 (100)
Japan Narrow Band Imaging Expert Team classification			0.36
1	7 (20.6)	15 (13.8)
2A	27 (79.4)	94 (86.2)
Confidence			0.007
High	22 (64.7)	42 (38.5)
Low	12 (35.3)	67 (61.5)
Treatment			0.16
Cold forceps polypectomy	21 (61.8)	81 (74.3)
Cold snare polypectomy	13 (38.2)	28 (25.7)

Values are presented as mean±standard deviation or number (%).

^a)According to the Paris classification.

Table 3.

Comparison between the “adenoma by initial section” and “adenoma by additional section” groups

Characteristic	Adenoma by additional section group (n=34)	Adenoma by initial section group (n=850)	p-value
Age (yr)	63.2±9.6	61.0±10.9	0.23
Sex			0.72
Male	18 (52.9)	477 (56.1)
Female	16 (47.1)	373 (43.9)
Location			0.04
Proximal	28 (82.4)	554 (65.2)
Distal	6 (17.6)	296 (34.8)
Size (mm)	2.65±0.48	3.77±0.15	<0.001
Morphology^a)			0.24
0–I	1 (2.9)	74 (8.7)
0–II	33 (97.1)	776 (91.3)
Japan Narrow Band Imaging Expert Team classification			<0.001
1	7 (20.6)	45 (5.3)
2A	27 (79.4)	787 (92.6)
2B	0 (0)	18 (2.1)
Confidence			<0.001
High	12 (35.3)	123 (14.5)
Low	22 (64.7)	727 (85.5)
Treatment			0.23
Cold forceps polypectomy	21 (61.8)	329 (38.7)
Cold snare polypectomy	13 (38.2)	502 (59.1)
Endoscopic mucosal resection	0 (0)	19 (2.2)

Values are presented as mean±standard deviation or number (%).

^a)According to the Paris classification.

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Efficacy of additional tissue sections for diminutive colorectal adenomas pathologically diagnosed as normal mucosa: a retrospective, cross-sectional study in Japan

Clin Endosc. 2025;58(4):577-585. Published online July 7, 2025

DOI: https://doi.org/10.5946/ce.2024.265

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Efficacy of additional tissue sections for diminutive colorectal adenomas pathologically diagnosed as normal mucosa: a retrospective, cross-sectional study in Japan

Fig. 1. Representative endoscopic images. An adenoma was detected using white-light imaging (A) and assigned a high level of confidence using narrow-band imaging (B). Another adenoma was detected using texture and color enhancement imaging (C) and was assigned a low level of confidence using narrow-band imaging (D).

Fig. 2. Flowchart of polyp enrollment.

Graphical abstract

Fig. 1.

Fig. 2.

Graphical abstract

Efficacy of additional tissue sections for diminutive colorectal adenomas pathologically diagnosed as normal mucosa: a retrospective, cross-sectional study in Japan

Characteristic	Total (n=993)	Normal mucosa by initial section group (n=143)	Adenoma by initial section group (n=850)	p-value
Age (yr)	60.9±10.9	59.7±10.8	61.0±10.9	0.21
Sex				0.11
Male	547 (55.1)	70 (49.0)	477 (56.1)
Female	446 (44.9)	73 (51.0)	373 (43.9)
Location				0.08
Proximal	658 (66.3)	104 (72.7)	554 (65.2)
Distal	335 (33.7)	39 (27.3)	296 (34.8)
Size (mm)	3.57±0.14	2.37±0.18	3.77±0.15	<0.001
Morphology^a)				<0.001
0–I	75 (7.6)	1 (0.7)	74 (8.7)
0–II	918 (92.4)	142 (99.3)	776 (91.3)
Japan Narrow Band Imaging Expert Team classification				<0.001
1	67 (6.7)	22 (15.4)	45 (5.3)
2A	908 (91.4)	121 (84.6)	787 (92.6)
2B	18 (1.8)	0 (0)	18 (2.1)
Confidence				<0.001
High	791 (79.7)	64 (44.8)	727 (85.5)
Low	202 (20.3)	79 (55.2)	123 (14.5)
Treatment				<0.001
Cold forceps polypectomy	431 (43.4)	102 (71.3)	329 (38.7)
Cold snare polypectomy	543 (54.7)	41 (28.7)	502 (59.1)
Endoscopic mucosal resection	19 (1.9)	0 (0)	19 (2.2)

Characteristic	Adenoma by additional section group (n=34)	Normal mucosa by both sections group (n=109)	p-value
Age (yr)	63.2±9.6	58.6±10.9	0.06
Sex			0.59
Male	18 (52.9)	52 (47.7)
Female	16 (47.1)	57 (52.3)
Location			0.15
Proximal	28 (82.4)	76 (69.7)
Distal	6 (17.6)	33 (30.3)
Size (mm)	2.65±0.48	2.27±0.18	0.17
Morphology^a)			0.07
0–I	1 (2.9)	0 (0)
0–II	33 (97.1)	109 (100)
Japan Narrow Band Imaging Expert Team classification			0.36
1	7 (20.6)	15 (13.8)
2A	27 (79.4)	94 (86.2)
Confidence			0.007
High	22 (64.7)	42 (38.5)
Low	12 (35.3)	67 (61.5)
Treatment			0.16
Cold forceps polypectomy	21 (61.8)	81 (74.3)
Cold snare polypectomy	13 (38.2)	28 (25.7)

Characteristic	Adenoma by additional section group (n=34)	Adenoma by initial section group (n=850)	p-value
Age (yr)	63.2±9.6	61.0±10.9	0.23
Sex			0.72
Male	18 (52.9)	477 (56.1)
Female	16 (47.1)	373 (43.9)
Location			0.04
Proximal	28 (82.4)	554 (65.2)
Distal	6 (17.6)	296 (34.8)
Size (mm)	2.65±0.48	3.77±0.15	<0.001
Morphology^a)			0.24
0–I	1 (2.9)	74 (8.7)
0–II	33 (97.1)	776 (91.3)
Japan Narrow Band Imaging Expert Team classification			<0.001
1	7 (20.6)	45 (5.3)
2A	27 (79.4)	787 (92.6)
2B	0 (0)	18 (2.1)
Confidence			<0.001
High	12 (35.3)	123 (14.5)
Low	22 (64.7)	727 (85.5)
Treatment			0.23
Cold forceps polypectomy	21 (61.8)	329 (38.7)
Cold snare polypectomy	13 (38.2)	502 (59.1)
Endoscopic mucosal resection	0 (0)	19 (2.2)

Table 1. Patient and polyp characteristics

Values are presented as mean±standard deviation or number (%).

According to the Paris classification.

Table 2. Comparison between the “adenoma by additional section” and “normal mucosa by both sections” groups

Values are presented as mean±standard deviation or number (%).

According to the Paris classification.

Table 3. Comparison between the “adenoma by initial section” and “adenoma by additional section” groups