Introduction
Advancement of endoscopic imaging technologies in the recent years has led to the
development of image enhanced endoscopy (IEE). Although histopathological examination
remains the gold standard for the diagnosis of lesions found in the gastrointestinal
(GI) tract [1], IEE allows optimization of the detection and diagnosis of dysplasias and cancers.
More commonly applied IEE technologies are magnifying endoscopy with narrow band imaging
(NBI) and chromoendoscopy [2].
To date, several diagnostic classifications have been advocated due to the high diagnostic
performance of each criteria, causing some confusion among endoscopists as to which
classification to use. To address this, each society or expert team moved to unify
and reorganize the past advocated classifications. For esophagus, Inoue’s Classification
(2000) and Arima Classification (2004) have been unified into the Japan Esophageal
Society (JES) magnifying endoscopic classification (2012). For stomach, the Vascular
Surface (VS) Classification (2001) [3] was rearranged to Magnifying endoscopy simple diagnostic algorithm for early gastric
cancer (MESDA-G) (2016) [4]. For the colon, Sano’s classification (2006) [5]
[6], Hiroshima (2008) [7], Showa (2009) [8], Jikei (2009) [9], NBI international colorectal endoscopic (NICE) (2010) [10]
[11] were proposed to be unified into Japan NBI Expert Team (JNET) classifications (2016)
[12]. However, these diagnostic criteria still differ between each organ by having different
categorizations. Current organ-specific classifications are well-accepted by specialized
expert endoscopists but may still pose confusion for general gastroenterologists.
Bearing this in mind, the idea of generalizing the practical use of image enhanced
magnifying endoscopy diagnostic criteria seemed quite appealing, hence, our group
proposed the Unified Magnifying Endoscopic Classification (UMEC) which can be applied
either in esophagus, stomach, or colon. In brief, we simplified the magnifying endoscopic
classification by dividing into three categories: Non-neoplastic, intramucosal neoplasia,
and deep submucosal invasive cancer. The aim of this feasibility pilot study was to
evaluate the diagnostic performance of UMEC using our clinical data.
Methods
Study population
This was a retrospective analysis of data collected prospectively at a single tertiary
referral center, Showa University Koto Toyosu Hospital, Tokyo, Japan between April
2014 and March 2020. Endoscopic images from patients who underwent magnifying NBI
examination of the esophagus, stomach, and colon were reviewed.
Image selection and data analysis
In this feasibility study, endoscopic images of patients who underwent magnifying
NBI of the esophagus, stomach and colon were retrieved. Of these, only cases with
corresponding histopathological results were selected and included. Images were then
grouped based on the histopathological diagnosis and separate folders per case were
created. Subsequently, white-light and non-magnifying images were deleted, and an
all-magnifying NBI image catalog was created. Image quality was assessed by rating
each image from 1 to 5, and was based on the clarity of the visual field and the microvascular
structure (1 being the lowest quality – blurred/unclear visual field with obscured
microvascularity, and 5 having the highest quality – clear visual field with no obstruction,
clear microvascularity). Images with ratings of 1 or 2 from the evaluators were excluded
from this study.
Two magnifying NBI images were selected per case and inserted into PowerPoint (Windows
2010; Microsoft, Santa Clara, California, United States) presentation slides against
a black background while preserving the file size, format and image quality. Each
case was assigned a number and subsequently arranged randomly according to random
number tables created by Excel (Windows 2010; Microsoft).
Randomized magnifying NBI images were then assessed separately by two endoscopists,
with experience in magnifying NBI, who were blinded to patients’ clinical information,
white-light and non-magnifying NBI findings as well as histopathological results.
In this study, an expert endoscopist was defined as an endoscopist who specialized
in a specific organ and was a board-certified trainer of the Japan Gastroenterological
Endoscopy Society. A general gastroenterologist (non-expert endoscopist) was defined
as an endoscopist who did not specialize in a specific organ even if he or she had
experience with magnifying NBI. The two endoscopists who participated in this study
were considered as non-experts.
Biopsy specimens were available for all cases, however, for carcinomas, histopathologic
diagnosis was made on endoscopically or surgically resected specimens. Specimens were
fixed in paraffin, stained with hematoxylin and eosin, and evaluated by an expert
pathologist in our institution. The expert pathologist diagnosed the specimens according
to the following: 1) esophageal specimens – Japanese Classification of Esophageal
Cancer, 11th edition, 2) gastric specimens – Japanese Classification of Gastric Carcinoma, 15th edition, and 3) colonic specimens – Japanese Classification of Colorectal, Appendiceal
and Anal Carcinoma, 9th edition. The accuracy of UMEC-based diagnosis was assessed while using the gold standard
histopathology as a reference.
Unified magnifying endoscopic classification (UMEC)
Through an adaptation of previous classifications for each respective organ (JES Classification
for esophagus, VS Classification and MESDA-G for stomach, and JNET Classification
for colon), UMEC was created as follows ([Table 1]).
Table 1
Outline of UMEC.
|
UMEC1
|
UMEC2
|
UMEC3
|
|
UMEC2A
|
UMEC2B
|
|
Expected histology
|
Non-neoplastic lesion
|
Intramucosal neoplasia
|
Deep submucosal invasive cancer
|
|
Benign
~
low grade neoplasia
|
High-grade neoplasia
~
Intramucosal cancer
(shallow submucosal cancer)
|
|
Esophagus
|
|
E-UMEC1
|
E-UMEC2A
|
E-UMEC2B
|
E-UMEC3
|
|
Endoscopic finding
|
IPCL
|
Normal IPCL
(The caliber of the vessels is about 7–10 μm)
|
Abnormal microvessels without severe irregularity
(The caliber of the vessels is about 7–10 μm)
|
Abnormal microvessels with severe irregularity or highly dilated abnormal vessels
(The caliber of the vessels is around 20 μm)
|
Highly dilated vessels which calibers appear to be more than three times that of usual
E-UMEC2B vessels
(The caliber of the vessels is often > 60 μm)
|
|
AVA
|
–
|
–
|
AVA-small, middle
(smaller than 3 mm)
|
AVA-large
(3 mm or larger)
|
|
Expected histology
(invasion depth)
|
Normal epithelium
|
Inflammation and LGIN
|
HGIN and SCC
(T1a-EP, T1a-LPM, T1a-MM, T1b-SM1)
|
invasive SCC
(T1b-SM2 or deeper)
|
|
Stomach
|
|
S-UMEC 1/2A
|
S-UMEC 2B/3
|
|
Endoscopic finding
|
DL
|
Absent
|
Present
|
Present
|
|
Vascular and surface
|
–
|
Regular
|
Irregular microvascular pattern and/or Irregular microsurface pattern
|
|
Expected histology
|
Non-cancer
|
Cancer
|
|
Colon
|
|
C-UMEC1
|
C-UMEC2A
|
C-UMEC2B
|
C-UMEC3
|
|
Endoscopic findings
|
Vessel
|
Invisible
|
Regular caliber
Regular distribution
|
Variable caliber
Irregular distribution
|
Loose vessel areas
Interruption of thick vessels
|
|
Surface
|
Regular dark
White spots similar to surrounding normal mucosa
|
Regular (tubular/branched/papillary)
|
Irregular or obscure
|
Amorphous areas
|
|
Expected histology
|
Hyperplastic polyp
Sessile serrated lesion (SSL)
|
Adenoma
Low-grade dysplasia
|
High-grade dysplasia/mucosal cancer
Shallow SM invasive cancer
|
Deep SM invasive cancer
|
UMEC, Unified Magnifying Endoscopic Classification; IPCL, intrapapillary capillary
loop; AVA, avascular area; LGIN, low-grade intramucosal neoplasia; EP, epithelium;
LPM, lamina propria mucosa; MM, muscularis mucosa; SM, submucosa; HGIN, high-grade
intramucosal neoplasia SCC, squamous cell carcinoma; DL, demarcation line.
Esophagus: UMEC diagnosis for the esophagus was categorized according to the characteristics
of intrapapillary capillary loop (IPCL) pattern and can be classified intothree3 groups
([Fig. 1]). E-UMEC 1 was considered non-neoplastic, E-UMEC 2A as inflammation and low-grade
intramucosal neoplasia, UMEC 2B as high-grade intramucosal neoplasia and intramucosal
cancer, and E-UMEC 3 as invasive cancer.
Fig. 1 UMEC for esophagus (E-UMEC). a E-UMEC 1 are considered non-neoplastic, b E-UMEC 2A as inflammation and low-grade intramucosal neoplasia, c UMEC 2B as high-grade intramucosal neoplasia and intramucosal cancer, and d E-UMEC 3 as invasive cancer.
Stomach: UMEC diagnosis for the stomach was made by assessing the presence or absence
of demarcation line (DL), irregular microvascular pattern (IMVP) and irregular microsurface
pattern (IMSP), and was based on an adaptation of the VS Classification and MESDA-G.
In brief, S-UMEC 1/2A were considered as non-cancer and S-UMEC 2B/3 as cancer ([Fig. 2]). For the stomach, S-UMEC 1 and 2A were not divided because there was not enough
evidence that non-neoplastic and adenoma can be distinguished just by using image
enhanced magnifying endoscopy. Similarly, S-UMEC 2B and 3 were not divided because
there was not enough evidence that image enhanced magnifying endoscopy is clinically
useful to diagnose the depth of invasion.
Fig. 2 UMEC for stomach (S-UMEC). a S-UMEC 1/2A are considered as non-cancer and b S-UMEC 2B/3 as cancer.
Colon: UMEC for the colon followed the JNET classification, which uses magnifying
NBI observation with a focus on vessel and surface patterns to diagnose colorectal
tumors as C-UMEC 1, 2A, 2B and 3 ([Fig. 3]). C-UMEC 1, 2A, 2B, and 3 correlate with the pathological diagnosis of hyperplastic
polyp and sessile serrated polyp, low-grade intramucosal neoplasia, non-invasive high-grade
neoplasia/intramucosal carcinoma/carcinoma in situ (Tis), and superficial submucosal
invasive carcinoma (SM-s: T1a; < 1,000 µm), and deep submucosal invasive carcinoma
(SM-d: T1b; ≥ 1,000 µm), respectively.
Fig. 3 UMEC for colon (C-UMEC). a C-UMEC 1 are considered as hyperplastic polyp and sessile serrated polyp, b C-UMEC 2A as low-grade intramucosal neoplasia, c C-UMEC 2B as non-invasive, high-grade neoplasia/intramucosal carcinoma/carcinoma
in situ (Tis), and superficial submucosal invasive carcinoma (SM-s: T1a; < 1,000 µm),
and d C-UMEC 3 as deep submucosal invasive carcinoma (SM-d: T1b; ≥ 1,000 µm).
Statistical analysis
Sensitivity, specificity, positive predictive value, negative predictive value, accuracy
for diagnosis of three categories – non-neoplastic, intramucosal neoplasia, and deep
submucosal invasive cancer – were calculated separately for each endoscopist. The
Kappa statistic for the two raters were used to estimate the interobserver agreement.
Kappa values ≤ 0.40, 0.41 to 0.75, and ≥ 0.75 were considered poor, good, and excellent,
respectively [13]. 95 % confidence intervals were calculated using the Wilson method. All analyses
were performed using STATA software version 14.1 (Stata Corp. Texas, United States).
Ethical considerations
The study protocol adhered to the principles of the Declaration of Helsinki and was
approved by the Ethics Committee of Showa University Koto Toyosu Hospital (IRB Registration
No: 20T7016).
Results
Esophagus
A total of 88 esophageal squamous lesions were included in the study after excluding
29 cases with low quality images. Population characteristics are presented in [Table 2]. Histopathological results were as follows: nine normal, 14 inflammation, 22 intraepithelial
neoplasia, and 43 SCC. The diagnostic ability for esophageal squamous lesion was evaluated
and summarized in [Table 3]. The ability of UMEC to diagnose esophageal squamous lesions was calculated and
is shown in [Table 3]. The sensitivity, specificity, and accuracy of UMEC for the diagnosis of SCC were
84.5 %, 84.9 %, and 84.7 %, respectively. The interobserver agreement, Kappa statistic = 0.51
(95 % CI: 0.35–0.66), was good. The sensitivity, specificity, and accuracy of UMEC
for diagnosis of squamous neoplasms were 87.0 %, 91.6 %, and 90.4 %, respectively.
The interobserver agreement, Kappa statistic = 0.59 (95 % CI: 0.40–0.77), was good.
When the diagnostic ability of UMEC for deep submucosal cancer was evaluated, the
sensitivity, specificity, and accuracy were 68.2 %, 94.4 %, and 91.5 %, respectively.
The interobserver agreement, Kappa statistic = 0.56 (95 % CI: 0.32–0.80), was good.
Table 2
Patient clinicopathological characteristics.
|
Variables
|
Esophagus (n = 88)
|
Stomach (n = 90)
|
Colon (n = 125)
|
|
Age (year), mean (SD)
|
65 (13)
|
75 (12)
|
64 (13)
|
|
Sex
|
|
|
63 (72 %)
|
67 (74 %)
|
73 (58 %)
|
|
|
25 (28 %)
|
23 (26 %)
|
52 (42 %)
|
|
Macroscopic type of cancer lesions
|
0-I = 5
0-IIa = 8
0-IIb = 19
0-IIc 11
|
Ip + IIa = 1
IIa = 11
IIa + IIc = 3
IIc = 24
|
Is = 15
Isp = 19
Ip = 1
IIa = 20
IIc = 1
|
|
Treatment of cancer lesions
|
|
|
48
|
39
|
22
|
|
|
5
|
0
|
24
|
|
Lesion diameter (mm) of cancer lesions, median (IQR)
|
10 (5–22)
|
17.5 (10–30.5)
|
11.0 (6–39)
|
|
Histopathology
|
Normal = 9
Inflammatory change = 14
Intraepithelial neoplasia = 22
Squamous cell carcinoma = 43
|
Gastritis = 26
Adenoma = 25
Adenocarcinoma = 39
|
Hyperplastic polyp (sessile serrated polyp) = 32
Low-grade intramucosal neoplasia = 47
Noninvasive high-grade neoplasia (intramucosal carcinoma, carcinoma in situ) = 15
(Submucosal) carcinoma = 31
|
|
Invasion depth
|
|
|
EP = 21/ LPM = 6/ MM = 5
|
31
|
15
|
|
|
9
|
3
|
8
|
|
|
2
|
5
|
23
|
SD, standard deviation; IQR, interquartile range; EP, epithelium; LPM, lamina propria
mucosa; MM, muscularis mucosa.
Table 3
Diagnostic yield of magnifying NBI applying UMEC for esophageal lesions.
|
Sensitivity
% (95 % CI)
|
Specificity
% (95 % CI)
|
PPV
% (95 % CI)
|
NPV
% (95 % CI)
|
Accuracy
% (95 % CI)
|
Kappa value
(95 % CI)
P value
|
|
E-UMEC 1 vs 2 + 3 (non-neoplastic vs neoplastic)
|
|
Endoscopist A
|
91.3 (77.4–97.4)
|
90.8 (85.8–92.9)
|
77.8 (65.9–83.0)
|
96.7 (91.5–99.0)
|
90.9 (83.6–94.1)
|
0.59 (0.40–0.77) P < 0.0001
|
|
Endoscopist B
|
82.6 (67.9–91.5)
|
92.3 (87.1–95.5)
|
79.2 (65.1–87.7)
|
93.8 (88.5–97.0)
|
89.8 (82.1–94.4)
|
|
E-UMEC 1 + 2A vs 2B + 3 (non-cancer vs cancer)
|
|
Endoscopist A
|
73.3 (66.1–75.2)
|
97.7 (90.1–99.6)
|
97.1 (87.4–99.5)
|
77.8 (71.7–79.3)
|
85.2 (77.8–87.1)
|
0.51 (0.35–0.66)
P < 0.0001
|
|
Endoscopist B
|
95.6 (87.7–98.7)
|
72.1 (63.9–75.4)
|
78.2 (71.7–80/8)
|
93.9 (83.2–8.3)
|
84.1 (76.0–87.3)
|
|
E-UMEC 1 + 2 vs 3 (Deep submucosal invasive cancer vs others)
|
|
Endoscopist A
|
81.8 (56.3–94.6)
|
90.0 (87.3–92.7)
|
56.3 (38.7–65.0)
|
97.2 (93.3–99.2)
|
89.8 (83.4–93.0)
|
0.56 (0.32–0.80)
P < 0.0001
|
|
Endoscopist B
|
54.5 (33.6–62.0)
|
98.7 (95.7–99.8)
|
85.7 (52.8–97.4)
|
93.8 (91.0–94.8)
|
93.2 (87.9–95.0)
|
NBI, narrow-band imaging; UMEC, unified magnifying endoscopic classification; PPV,
positive predictive value; NPV, negative predictive value; CI, confidence interval.
Stomach
From 150 cases, 60 cases with low-quality images were excluded from this study. A
total of 90 gastric lesions were included to this study. Population characteristics
are presented in [Table 2]. Upon histopathological examination, 51 were diagnosed as non-cancer, and 39 as
cancer. The sensitivity, specificity and accuracy of UMEC for the diagnosis of gastric
cancer (S-UMEC 1/2A vs UMEC 2B/3) were calculated and shown in [Table 4]. The overall sensitivity, specificity, and accuracy of UMEC for both endoscopists
were 90.9 %, 89.2 %, and 89.5 %, respectively. The interobserver agreement, Kappa
statistic = 0.73 (95 % CI: 0.59–0.87), was good.
Table 4
Diagnostic yield of magnifying NBI applying UMEC for gastric lesions.
|
Sensitivity
% (95 % CI)
|
Specificity
% (95 % CI)
|
PPV
% (95 % CI)
|
NPV
% (95 % CI)
|
Accuracy
% (95 % CI)
|
Kappa value
(95 % CI)
P value
|
|
S-UMEC 1/2A vs 2B/3 (non-cancer vs cancer)
|
|
Endoscopist A
|
84.6 (76.8–86.7)
|
98.0 (92.1–99.6)
|
97.1 (88.1–99.5)
|
89.3 (83.8–90.7)
|
92.2 (85.4–94.0)
|
0.73 (0.59–0.87)
P < 0.001
|
|
Endoscopist B
|
97.1 (87.5–99.5)
|
80.4 (74.5–81.8)
|
75.0 (67.6–76.9)
|
97.8 (90.8–99.6)
|
86.7 (79.4–88.5)
|
NBI, narrow-band imaging; UMEC, unified magnifying endoscopic classification; PPV,
positive predictive value; NPV, negative predictive value; CI, confidence interval.
Colon
From 150 cases, 25 cases with low-quality images were excluded from this study, and
a total of 125 colonic lesions were included to this study. Population characteristics
are presented in [Table 2]. Histologically, 32 were diagnosed as hyperplastic polyps, 47 as adenomas, and 15
as high-grade dysplasia, 8 as SM-s adenocarcinoma, and 23 as SM-d adenocarcinoma.
The diagnostic yield of UMEC for 1) non-cancer vs cancer, 2) non-neoplasm vs neoplasm,
and 3) deep submucosal invasive cancer were evaluated and are summarized in [Table 5]. The overall sensitivity, specificity, and accuracy of UMEC for colonic cancer were
79.4 %, 85.5 %, and 83.2 %, respectively. The interobserver agreement, Kappa statistic = 0.63
(95 % CI: 0.49–0.77), was good. The overall sensitivity, specificity, and accuracy
of UMEC for in the diagnosis of colonic neoplasms (C-UMEC 1 vs C-UMEC 2 + 3) were
90.6 %, 97.9 %, and 96.0 %, respectively. The interobserver agreement, Kappa statistic = 0.79
(95 % CI: 0.66–0.91), was good. Finally, the overall sensitivity, specificity, and
accuracy of UMEC for diagnosis of deep submucosal invasive cancer (C-UMEC 1 + 2 vs
3) were 80.5 %, 97.6 %, and 94.4 %, respectively. The interobserver agreement, Kappa
statistic = 0.66 (95 % CI: 0.49–0.83), was good.
Table 5
Diagnostic yield of magnifying NBI applying UMEC for colonic lesions.
|
Sensitivity
% (95 % CI)
|
Specificity
% (95 % CI)
|
PPV
% (95 % CI)
|
NPV
% (95 % CI)
|
Accuracy
% (95 % CI)
|
Kappa value
(95 % CI)
P value
|
|
C-UMEC 1 vs 2 + 3 (non-neoplastic vs neoplastic)
|
|
Endoscopist A
|
89.4 (76.9–96.5)
|
97.3 (90.6–99.7)
|
95.5 (84.5–99.4)
|
93.5 (85.5–97.9)
|
94.2 (88.4–97.6)
|
0.80
(0.69–0.90)
P < 0.001
|
|
Endoscopist B
|
91.5 (79.6–97.6)
|
100 (92.8–100)
|
100 (88.0–100)
|
94.9 (87.4–98.6)
|
96.7 (91.8–99.1)
|
|
C-UMEC 1 + 2A vs 2B + 3 (non-cancer vs cancer)
|
|
Endoscopist A
|
76.1 (61.2–87.4)
|
77.2 (66.4–85.9)
|
66.0 (51.7–78.5)
|
84.7 (74.3–92.1)
|
76.8 (68.4–83.9)
|
0.63
(0.49–0.77)
P < 0.001
|
|
Endoscopist B
|
82.6 (68.6–92.2)
|
93.7 (85.8–97.9)
|
88.4 (74.9–96.1)
|
90.2 (81.7–95.7)
|
89.6 (82.9–94.3)
|
|
C-UMEC 1 + 2 vs 3 (Deep submucosal invasive cancer vs others)
|
|
Endoscopist A
|
91.3 (72.0–98.9)
|
95.1 (88.9–98.4)
|
80.8 (60.6–93.4)
|
98.0 (92.9–99.8)
|
94.4 (88.8–97.7)
|
0.66
(0.48–0.83)
P < 0.001
|
|
Endoscopist B
|
69.6 (47.1–86.8)
|
100 (94.7–100)
|
100 (71.3–100)
|
93.6 (87.2–97.4)
|
94.4 (88.8–97.7)
|
NBI, narrow-band imaging; UMEC, unified magnifying endoscopic classification; PPV,
positive predictive value; NPV, negative predictive value; CI, confidence interval.
Discussion
The diagnostic performance and accuracy of UMEC to identify neoplasms and carcinomas
among endoscopically identified lesions was evaluated in this study. When compared
to the gold standard histopathology, UMEC showed satisfactory accuracy in diagnosing
non-neoplastic, intramucosal neoplasia, and deep submucosal invasive cancer.
The role of magnifying NBI differs in each organ. In the esophagus, it is used to
analyze the histopathology of squamous epithelium and the invasion depth of the cancer.
In the stomach, magnifying NBI plays a role in the assessment of the histopathology
of the columnar epithelium, for the differentiation between non-cancer and cancer.
Similar to the esophagus, in the colon, magnifying NBI is used to analyze the histopathology
of columnar epithelium and the invasion depth of the cancer. Although these differences
exist, applying the same categorization to each organ may be simpler and easy to understand.
In addition, UMEC does not aim to replace the existing organ-specific classifications
utilized by specialized expert endoscopists; however, a generalized use of a magnifying
NBI diagnostic criteria common to the gastroinestinal tract may be more practical
for non-expert endoscopists and general gastroenterologists, hence, the proposal of
UMEC in the present study.
Esophagus
Since the introduction of IPCL Pattern Classification by Inoue in 2007 [14], IPCL pattern has been applied to estimate histopathological atypia by use of magnifying
NBI [14]. By assessing the irregularity of IPCL, which refers to the changes in morphology
such as dilation, tortuosity, change in caliber, and various shapes, magnifying NBI
has been shown to accurately diagnose esophageal SCC [15]
[16]. Studies on the diagnostic performance of IPCL pattern classification and the invasion
depth have shown satisfactory results, with over 80 % rates [16]
[17]
[18]
[19]
[20]
[21]. In 2012, the Japan Esophageal Society (JES) established a classification of magnifying
NBI findings to diagnose ESCC and its invasion depth of superficial ESCC [22]. This newly developed JES magnifying endoscopic classification is useful in estimating
the invasion depth of superficial esophageal SCC and this classification has been
used in clinical practice in Japan but not yet being standardized elsewhere outside
of Japan.
From our experience, auxiliary criteria of assessing avascular area and reticular
pattern vessels are subjective and its interpretation is not standardized or categorized.
We have simplified the criteria as described in [Table 1]. Therefore, we recommend focusing on IPCL morphology. By utilizing UMEC, the overall
accuracy for diagnosis of SCC was 84.7 % and the overall accuracy for diagnosis of
deep submucosal invasion was 91.5 %, which seems to be comparable to previous studies.
Stomach
By utilizing magnifying NBI, the standard method of evaluating gastric lesions, VS
classification [3], and the diagnostic strategy for gastric mucosal cancer, MESDA-G [4], have been created to simplify the process of diagnosis and improve accuracy. Literature
reporting on the diagnostic performance of magnifying NBI with VS classification in
the diagnosis of early gastric cancer have shown satisfactory to excellent accuracy
rates, ranging from 79 % to more than 95 % [23]
[24]
[25]. In the present study, through an adaptation of MESDA-G, UMEC led to good diagnostic
accuracy (overall accuracy for both endoscopists: 89.5 %) and interobserver agreement
for distinguishing gastric cancer from non-malignant cases, coinciding with previous
reports.
In differentiating intramucosal cancer from submucosal invasive cancer, there is some
evidence that white light endoscopy and magnifying NBI (especially in differentiated
gastric cancer) is useful in diagnosing the invasion depth [26]
[27]
[28]
[29]; however, consensus is yet to be reached on this. This is because NBI shows only
the superficial mucosa for early gastric cancer and invasive tissue is often not exposed
at the surface and mucosal structures remain, even when the cancer invades the submucosa
[30], hence, making it difficult to differentiate intramucosal cancer from submucosal
invasive cancer. For this reason, the difference between gastric S-UMEC 2B and 3 could
not be evaluated in the present study.
Furthermore, undifferentiated cancer with non-cancerous epithelium on the mucosal
surface as well as pale mucosal lesion with tissue diagnosis of signet-ring cell carcinoma
are difficult to diagnose by magnifying NBI, since non-cancerous epithelium remains
on the mucosal surface. This implies that these specific lesions should also be regarded
as limitations in applying UMEC in the stomach [25].
Colon
To date, several magnifying NBI classifications of colorectal tumors have been advocated.
Sano et al were the first to publish a magnifying NBI classification known as the
Capillary Pattern classification in 2006 [6]. Based on this, other magnifying NBI classifications (Hiroshima [7]
[31], Showa [8], and Jikei [9] classifications) were proposed. In 2012, the NBI International Colorectal Endoscopic
(NICE) classification [10] was established as a simple classification which can be applied using NBI with or
without optical magnification, and is now being used worldwide. However, as histopathological
criteria of curative endoscopic resection for early CRC are being clarified, endoscopists
are required to diagnose the invasion depth accurately and obtain appropriate histopathological
materials by en bloc EMR or ESD. Therefore in 2016, the JNET classification [12] was proposed by the Japan NBI Expert Team, aiming to unify previous classifications
which provides accurate qualitative and quantitative diagnosis linking to the appropriate
treatment strategy including polypectomy, piecemeal/en bloc EMR, ESD, and surgery
[32]. Several studies have shown its diagnostic performance and clinical usefulness [33]
[34] and it is already widespread in Japan, and the International Evaluation of Endoscopy
classification JNET (IEE-JNET), a collaborative research project by ESGE and JGES,
is currently underway. Thus, our new UMEC classification, the main objective of which
is to unify classification among three organs, basically adapted the JNET classification.
In our study, the overall accuracy for diagnosis of CRC was 93.3 % and the overall
accuracy for diagnosis of deep submucosal invasion was 95.1 %. However, the accuracy
for type 2B lesions was relatively lower with poor intraobserver agreement, similar
to the previous studies [34]. Becausee chromoendoscopy, with the use of crystal violet staining, can provide
a more reliable diagnosis for invasion depth than IEE [35], it is recommended to also perform chromoendoscopy for Type 2B lesions [34]. In other words, due to the time associated with chromoendoscopy, UMEC is clinically
useful as a previous step to select which lesion should undergo chromoendoscopy as
part of the diagnostic strategy.
Limitations
At this point, however, certain study limitations must be acknowledged. This was a
retrospective observational study, which potentially included selection bias. Moreover,
this was an image review study in a single center, and a larger number of lesions
are needed to further validate the results obtained. In addition, direct comparison
of the diagnostic yield of previous criteria was not done in this study, and a prospective
study with a clinical setting is needed to validate these study results.
Conclusions
In all, given its good diagnostic accuracy in this pilot study, UMEC appears to be
a simple and practically acceptable classification, particularly to general gastroenterologists.
Furthermore, generalized use of magnifying NBI diagnostic criteria may be achieved,
hence, UMEC deserves further evaluation in future studies.
