Epithelial lesions (polyps) of the colon: issues of diagnosis and treatment

Epithelial lesions (polyps) of the colon: issues of diagnosis and treatment

Among oncological diseases, colorectal cancer (CRC) ranks 3rd in the world in terms of prevalence [1].In 70-75% of patients, CRC develops due to the adenoma-carcinoma sequence [2], and in 25-30% it arises from wide-based serrated lesions [3].In this regard, the detection and removal of colon epithelial lesions during colonoscopy is considered an important method of CRC prevention.Therefore, highquality colonoscopy with proper documentation and removal of detected colonic epithelial lesions have become the most important tasks of the endoscopist to reduce the incidence of CRC and its mortality [1,[4][5][6][7][8].
Numerous guidelines have been developed that regulate the performance of effective colonoscopy, detection and prevention of CRC development and address the indications for this procedure, criteria for its effectiveness [4][5][6], CRC screening [1], removal of colorectal lesions [7,8], and followup after polypectomy [9,10].
The European Society of Gastrointestinal Endoscopy (ESGE) has developed key quality indicators for lower digestive system endoscopy: the level of adequate colon preparation with mandatory assessment according to the Boston or Ottawa scale (minimum standard 90%); frequency of blind intubation and the time of colonoscope withdrawal (with intact intestine 6 minutes) with mandatory video and photo documentation (minimum standard 90%); frequency of adenoma detection (minimum standard 25%); proper polypectomy technique (minimum standard 80%), including assessment of morphology and depth of invasion, selection of an adequate technique for removing lesions, assessment of resection completeness, marking the site of removal of lesions larger than 2 cm, removal of lesions larger than 5 mm for pathological examination; complication rate (in the first 7 days after polypectomy, the readmission rate is 0.5%); assessment of patient perception of colonoscopy; and recommendations for follow-up after polypectomy [5].
The American Society for Gastrointestinal Endoscopy (ASGE)/American College of Gastroenterology (ACG), the European Union of Gastroenterology (UEG) and the Ukrainian Association of Endoscopists recommend that in addition to the above quality indicators, informed consent for colonoscopy should be obtained [4,11]; assess the frequency of compliance with the recommended follow-up periods after polypectomy and in patients with inflammatory bowel disease, the frequency of colon mucosal biopsy in patients with chronic diarrhoea, Crohn's disease/ulcerative colitis; the frequency of self-removal during colonoscopy of lesions up to 2 cm in size on the pedicle or broad base or referral of the patient to a more experienced specialist for endoscopic removal before referral for surgical treatment; the frequency of colonoscopy complications (perforation, bleeding) [4] (see Table ).
In the period after the procedure, it is necessary to record complications (perforation, bleeding), perform endoscopic treatment of complications, and document recommendations on the timing of repeat colonoscopy (after reviewing the histological data).
Priority indicators of colonoscopy quality include the frequency of adenoma detection; use of recommended intervals between colonoscopies performed for CRC screening in patients at average risk and follow-up after polypectomy and surgical treatment of cancer; and the frequency of colonic intubation with photographic documentation.Achievement of the target level of each of these indicators is closely related to important clinical outcomes [4].
Analysis of the quality of colonoscopy performance makes it possible to assess the quality of the endoscopist's work and, if the target levels of quality indicators are unsatisfactory, to take measures to improve them.Such measures include compliance with the time of device withdrawal, use of two-stage bowel preparation, visualisation of the proximal sides of the mucosal folds during device withdrawal, removal of excess fluid, mucus and colon contents and achievement of sufficient stretching of the colon [12].
The ASGE/ACG guidelines [4] state that endoscopists who cannot improve their performance and achieve the recommended adenoma detection rate through training and technical measures should be denied the opportunity to perform colonoscopy, as low adenoma detection rates put patients at risk (undetected polyps/early CRC).
The quality of colonoscopy depends on both the preparation of the intestine and the examination technique [5,13].A pathological area on the surface of the mucosa is detected without magnification and chromoscopy in the presence of elevation or depression, or discolouration of the mucosa, or a break in the network of surface capillaries [14].
The use virtual chromoendoscopy or dye-supplemented chromoendoscopy in addition to high-resolution whitelight endoscopy to detect residual neoplasia at the scar site after polypectomy in fragments; possible inclusion of artificial intelligence (for detection and characterisation of lesions) in colonoscopy.
According to the guidelines for the removal of colorectal lesions, the choice of the optimal method of lesion removal is influenced by its characteristics, namely, location, size, morphology, and histology [7,8,14].Accurate and precise characteristics are the key to achieving the main goal of polypectomy -complete and safe removal of colorectal lesions and definitive prevention of CRC.
For the assessment and characterisation of colorectal for adenomatous lesions without a pedicle (type 0-II and 0-Is according to the Paris classification) 10 mm, use the term "laterally spreading tumour" (LST) and describe their surface as granular or non-granular; Photographically document all lesions 10 mm in size before excision and the defect after resection; use electronic methods, such as narrow-spectrum imaging, iScan, Fuji Intelligent Chromoendoscopy (FICE) or blue-light imaging, or dye-enhanced endoscopy (chromoendoscopy) to predict lesion histology using optical diagnostic classifications; endoscopically detect deep submucosal invasion.
The Paris classification of colorectal lesions includes macroscopic type 0 -superficial lesions and macroscopic types 1-5 -advanced cancer.According to the updated Paris classification [15], the endoscopic morphology of superficial lesions of the colon mucosa can be assessed using a standard video endoscope after spraying a dye (indigocarmine solution), and the following types of superficial neoplastic lesions are identified: 0-I (polypoid) 0-Ir -on the leg, 0-Isp -on the half-leg, 0-Is -on a wide base (seated, higher closed forceps heights of 2.5 mm) 0-II (non-polypoid) 0-ІІa -elevated (lower heights of closed forceps 2.5 mm), 0-IIb -flat lesions that do not protrude above the surface of the mucous membrane, 0-IIc -slightly deepened/slight depression (less than 1.2 mm below the mucosa); III (non-polypoid) -undermined, inferior mucosa more than 1.2 mm (practically not found in the colon).
Non-polypoid lesions with a diameter of 10 mm are referred to as LST.They have a low vertical axis and extend laterally along the lumen wall.The Kudo classification is used to describe LSTs [17].Due to significant differences in the risk of invasive cancer, LSTs are divided into two types: granular (granular) -LST-G and non-granular (non-granular) -LST-NG.LST-G have a nodular surface and are divided into two subtypes: homogeneous -LST-G-Homogeneous (H) and mixed -LST-G-Mixed (M).LST-NG have a smooth surface, they are also divided into two subtypes: flat-raised -LST-NG-Flat-Elevated (F-E) and pseudo-depressed -LST-NG-Pseudo-Depressed (P-D).
After describing the colorectal lesion according to the Paris Classification, it is recommended to examine it to determine the type according to approved classifications that allow for a high probability of predicting the histology of the lesion.A number of studies, including several meta-analyses, have shown that optical diagnosis of colorectal lesions is feasible in routine clinical practice and comparable to histology [19,20].
The microarchitecture of the lesion surface and pitting pattern are assessed using narrow-spectrum imaging (iScan, FICE blue light imaging) or magnified endoscopy with chromoendoscopy and classified according to the NICE (Narrow-band imaging International Colorectal Endoscopic) classification [7,8].The NICE classification can be applied when using colonoscopes with or without magnification.This classification assesses the colour of the lesion, the regularity of the superficial vessels and the surface pattern.Its use is useful for assessing the most clinically relevant approaches: leave hyperplastic miniature lesions of the rectum and sigmoid colon; remove all adenomas anywhere in the colon and any serrated lesions proximal to the sigmoid colon and larger than 5 mm; perform a biopsy and refer the patient for surgical treatment if there is evidence of deep submucosal invasion [7].
The accuracy of this classification in the diagnosis of hyperplastic lesions of the rectosigmoid colon exceeds 90% [19].
A characteristic feature of adenoma is a depression in the surface topography, red in white light and brown in narrowspectrum imaging compared to other areas of the polyp surface.This feature is insensitive (<50%) but highly specific (>90%) for common adenoma in small ( 5 mm) colorectal lesions, and is likely to be a predictor of adenomatous histology in these lesions [21].
The US MSTF guidelines [7] state that other endoscopic classifications of colorectal lesions using the latest technologies require further study.
Recently, the Colorectal NEoplasia Endoscopic Classification to Choose the Treatment (CONECCT) classification was proposed, which combines the criteria of seven proven classifications used to characterise polyps into a single table with the same name [22].However, given that the use of the CONECCT classification requires special training of endoscopists and the correlation between histology and this classification remains insufficient, scientific societies have not yet recommended it for systematic use [23].
To characterise sessile serrated lesions, the criteria proposed by the Workgroup Serrated Polyps and Polyposis (WASP) are additionally applied.According to the WASP criteria, 4 features have been added to the NICE classification: cloud-like surface, indistinct borders, irregular shape and dark spots inside the crypts.These morphological features are used to differentiate between broad-based serrated lesions and hyperplastic lesions in NICE type 1 polyps.The presence of at least two of these NICE type 3 and Kudo Vn fossa patterns are specific for deep (greater than 1000 μm) invasion [7,8].Deep submucosal invasion in a lesion without a pedicle is associated with a significant risk of residual cancer in the bowel wall or lymph nodes after any form of endoscopic resection.Therefore, the US MSTF [7] recommends that if these signs are present, a cold biopsy of the part of the lesion with the above features should be performed, followed by a tattoo and referral to a surgeon.

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For stalkless lesions with superficial (less than 1000 μm) invasion of the submucosa, endoscopic resection is performed.However, there are no endoscopic signs to suggest superficial invasion of the submucosa.A non-rough (smooth) surface, especially in combination with a depressed (Paris classification type 0-IIc) or bulky (Paris classification type 0-Is) shape, is associated with an increased risk of superficial invasion.
Endoscopic resection in a single block (if possible, safely performed), followed by fixing the removed specimen on a flat surface (e.g., cork, foam) and cutting the lesion perpendicular to the resection plane, allows for accurate measurement of the depth of invasion.
To detect the potential presence of superficial submucosal invasion, ESGE also recommends the use of advanced advanced endoscopic imaging techniques.Narrow-spectrum imaging and higher-magnification chromoendoscopy have been shown to improve the identification of morphological features suggestive of submucosal invasion (such as irregular or absent superficial vessels) [8,30].Studies using narrowspectrum imaging have shown that the Sano IIIB, Hiroshima C3, and NICE 3 capillary patterns are highly indicative of deep invasion [8,31].Studies using magnification chromoendoscopy have shown that the shape of Kudo Vn pits is associated with a high probability of deep invasion into the submucosa [8,32].Sano IIIA pattern and Kudo Vi fossa shape are prognostic factors for superficial submucosal invasive carcinoma and, therefore, can be used to identify patients who are indicated for resection with a single block [8].
After assessing the morphology of the lesion according to the Paris, NICE, WASP classifications and determining the risk of submucosal invasion, lesions to be removed endoscopically are removed using the safest, most complete or most effective resection techniques based on available evidence.An algorithm for the treatment of colorectal lesions was proposed by the US MSTF [7] (Fig. 2).

Removal of tiny ( 5 mm) and small (6-9 mm) lesions
Use cold polypectomy to remove tiny ( 5 mm) and small (6-9 mm) lesions due to its high complete resection rate and safety profile.
Do not use cold-loop polypectomy to remove small lesions ( 5 mm) because of the high incidence of incomplete resection.For lesions 2 mm, if cold-loop polypectomy is technically difficult, large-capacity forceps can be used.
Do not use hot biopsy forceps for polypectomy of tiny ( 5 mm) and small (6-9 mm) lesions due to the high incidence of incomplete resection, inadequate histopathological specimens, and complications.
In addition to recommendations, the US MSTF [7] provides videos and photos describing the technique of a particular technique, which is also useful for the endoscopist.
Endoscopists who already have some experience in performing colonoscopy and want to master polyp removal techniques can start with cold loop polypectomy.The technique is simple and safe, which has been proven by many studies, and is well described in this article.

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After removal of the lesion with a cold loop, a structure similar to a vessel can be found in the wound, but it is a submucosal layer gathered in a "bundle" (Fig. 3).This situation is safe and requires no further action.

Lesions without a stem (10 -19 mm)
To remove these lesions, perform a cold or hot loop polypectomy with or without submucosal injection.
The optimal methods for removing broad-based lesions of 10 to 19 mm remain uncertain.However, endoscopic mucosal resection should be considered for non-polypoid and serrated lesions between 10 and 19 mm in size, as it is more convenient and allows for a higher rate of complete removal and is associated with a low recurrence rate [33].
In contrast to the US MSTF [7], ESGE for the removal of broad-based lesions/ lesions of 10-19 mm in size only offers hot-loop polypectomy with or without submucosal injection.It is noted that in most patients, deep thermal injury is a potential risk, and therefore submucosal injection should be considered before the intervention [8] (Fig. 4).
Lesions without a pedicle ( 20 mm) Endoscopic mucosal resection is the preferred treatment for these colorectal lesions.It can provide complete resection and avoid the higher morbidity, mortality and cost associated with alternative surgical treatment.
Treatment of large ( 20 mm) colorectal lesions without a pedicle is performed by an endoscopist with sufficient polypectomy experience.

Fig. 4. Stages of LST-G-H removal of the sigmoid colon: A -lesion in white light, B -in FICE mode, the lesion is defined as NICE type 2; C -during submucosal injection, the structure of the NICE type 2 lesion is clearly defined; D -a loop is applied to the lesion with the surrounding normal mucosa; E -the lesion is removed, unchanged mucosa around the pathological tissue is visualised; F -post-resection wound, no residual tissue is visualised. Pathological conclusion: tubular adenoma of the colon (ICD-O code 8211/0).
High-grade glandular epithelial dysplasia was not detected.No invasive neoplastic process was detected.
No glandular epithelial dysplasia was detected at the resection margins (lesion was completely removed).Use a contrast agent, such as indigo carmine or methylene blue, in the submucosal injection solution to facilitate recognition of the submucosa and muscle lamina.
Do not use tattoo solution (sterile suspension of carbon particles) as a submucosal injection solution.The carbon particle suspension may lead to submucosal fibrosis, which may reduce the technical success of future endoscopic resection of residual or recurrent lesions.
Use a viscous injectable solution, such as hydroxyethyl starch, for lesions 20 mm to remove them in fewer pieces and to reduce the procedure duration compared to that of normal saline.
Do not use ablative methods, such as argon plasma coagulation, soft loop tip coagulation, on endoscopically visible residual tissue of the lesion, as they are associated with an increased risk of recurrence.
Use adjuvant thermal marginal ablation after endoscopic mucosal resection where no endoscopically visible adenoma remains despite careful inspection.There is currently insufficient evidence to recommend argon plasma coagulation or soft loop tip coagulation.The latter method is difficult to apply and can be safely used by experienced endoscopists.
Detailed examination of the post-resection mucosal defect to determine signs of immediate or delayed risk of perforation and, accordingly, to perform endoscopic clip suturing.
Prophylactic suturing of resection defects 20 mm in size in the right half of the colon with clips, whenever possible.
Treatment of intra-procedural bleeding with endoscopic coagulation (coagulation forceps or soft loop tip coagulation) or mechanical therapy (clip) with or without combined use of dilute epinephrine injection.
Patients taking antithrombotic medications who are candidates for endoscopic removal of colorectal lesions 20 mm should be individually assessed, balancing the risks of interrupting anticoagulation therapy for colonoscopic polypectomy or mucosal resection against the risks of significant bleeding during and after the procedure.
Endoscopic mucosal injection and incision resection as a simple technique is widely used to remove large lesions without a pedicle [34].Lesions less than 20 mm can usually be removed in a single unit if an electrosurgical device is used, whereas lesions 20 mm are more often removed in parts.
Submucosal injection is a key step in endoscopic mucosal resection.For submucosal injection, saline is the most commonly available solution, but it has the disadvantage that it is rapidly absorbed and therefore must be frequently re-injected into the submucosa.For endoscopic resection of mucosal lesions, especially those larger than 20 mm, it is better to use colloidal solutions (sodium hyaluronate, 50% dextrose solution, hydroxyethyl starch, succinylated gelatin and a mixture of fibrinogen).Hydroxyethyl starch solutions are available in Ukraine.An injection with the addition of indigocarmine is preferable [7].
The US MSTF guidelines [7] describe a dynamic submucosal injection technique that creates a large injection "cushion" under the lesion, even when saline is used.During the injec-tion, the fluid is directed into the submucosa by slowly deflecting the tip of the endoscope towards the opposite wall, combined with gentle pulling back of the catheter needle and suction to desufflate the lumen [7].A rigid loop is used to facilitate tissue capture.After the loop has captured the lesion, it is necessary to ensure that the muscle plate is not captured.To do this, the lumen is inflated with air to stretch the wall, the loop is lifted upwards and slightly loosened.Only then is the loop completely closed and the lesion removed by electrocoagulation.In addition to a detailed description of this technique, photos and videos are included.
When performing endoscopic mucosal resection, it is necessary to remove all visible lesion tissue completely within a single colonoscopy session and with a safely minimal number of fragments.Previous unsuccessful attempts to remove the lesion or the use of a loop or argon plasma coagulation on endoscopically visible residual lesions have been shown to increase the risk of recurrence [7,35].However, if the resection is performed in fragments and the edges are free of visible residual pathological tissue, then ablation of the defect edges using argon plasma coagulation or soft loop coagulation can burn microscopic residual tissue and thereby reduce the risk of recurrence [7,36].
However, according to the ESGE guidelines, the role of adjuvant thermal margin ablation after endoscopic mucosal resection, where there is no endoscopically visible adenoma tissue on close inspection, needs further evaluation [8].
For removal of epithelial lesions of the colon mucosa, endoscopic dissection of the submucosa is also used, a type of endoscopic mucosal resection when the lesion is completely immersed in water ("underwater"), cold-loop resection of large lesions (20 to 40 and even up to 60 mm), a combination of endoscopic mucosal resection and endoscopic dissection of the submucosal layer, endoscopic full-layer resection [7].These techniques are more complex, can be performed only by experienced doctors, and require expensive equipment.
Lesions on the leg Perform hot loop polypectomy to remove these lesions (US MSTF: head less than 20 mm, pedicle less than 5 mm; ESGE: head less than 20 mm, pedicle less than 10 mm).
Prophylactic mechanical ligation of the pedicle with a removable loop (Fig. 5) or clips for polyps with a head 20 mm or pedicle thickness 5 mm to prevent bleeding during polypectomy and delayed bleeding afterwards (US MSTF: head 20 mm, pedicle 5 mm; ESGE: head 20 mm, pedicle 10 mm).
Remove polyps on the pedicle from the intestinal lumen in a single block to allow for assessment of the resection margins, rather than fragmenting the polyp heads to remove them through an endoscope.
Features The incision should be made in the area from the middle to the lower part of the pedicle to obtain an adequate sample for histological assessment of pedicle invasion [7].
The injection of 4-8 ml of epinephrine 1:10,000 into both the polyp head and pedicle (Fig. 6) can reduce the size of the UJCS.2023 July/August; 90(4) The Ukrainian Journal of Clinical Surgery polyp and increase the resection rate with a single block [37].
Prophylactic clip placement in lesions with a large pedicle can be difficult and lead to thermal damage at the clip site.In such situations and when it is impossible to apply a loop to ligate the polyp pedicle, the clip is placed immediately after the pedicle is crossed [7].
The colonoscopy report should include photographic documentation of the colorectal lesion before and after removal; indicate the method of resection used.Thus, in order to reduce the incidence of CRC and its mortality, it is necessary to perform high-quality colonoscopy with the detection and removal of colorectal lesions using modern methods.Adherence to the recommendations of the world's leading gastrointestinal endoscopy experts on performing effective diagnostic colonoscopy and the use of advanced methods of endoscopic resection of detected lesions significantly increase the effectiveness of colonoscopy, which in turn leads to a decrease in the incidence of CRC.
Funding.The author has not received any remuneration in any form that may have influenced the coverage of this article.
Conflict of interest.The author has declared no conflict of interest.

References
Fig. 5. Removal of a lesion on the leg using a loop for ligation of the leg to prevent bleeding.The pathological conclusion is similar to that of Fig. 4, including the level of invasion.

Fig. 6. Stages of lesion removal (type 0-Ir according to the Paris classification) on a thick pedicle:
A -the pedicle of the lesion; B -injection of the solution into the base of the pedicle; C -a loop applied to the pedicle of the lesion; D -the pedicle after resection with a hot loop.Pathological conclusion: adenocarcinoma of the colon (ICD-O code 8140/3) of low grade -lowgrade (G1-G2 in the previous grading system), developed in a tubular villous adenoma; pT1 L0 V0 Pn0 R0.The level of invasion is 1 according to Haggitt.Macroscopic description: polyp-like lesion on the pedicle, with a large tuberous surface, brown in colour, total size 2.5 2 1.8 cm, pedicle 0.4 cm long, 0.8 cm in diameter.

А C B D
features is considered sufficient for the diagnosis of widebased serrated lesions[24].If a serrated lesion shows areas with a clear change in surface pattern (NICE type 2 features) or a nodular component, this is indicative of cytological dysplasia[25].Identification of high-risk lesions may influence endoscopic therapeutic strategy and surveillance recommendations[26].The vertical depth of invasion of submucosal cancer can be assessed on the basis of morphological manifestations using high-resolution endoscopy without magnification[7].It may indicate the presence of submucosal invasive carcinoma:lesions of type 0-IIc and 0-IIa + 0-IIc according to the Paris classification; non-granular surface (especially the pseudo-depression subtype); NICE type 3 [27] and Kudo V dimple pattern [28]; redness, dense consistency, deep depressed area (Fig.1), white spots similar to chicken skin, and convergence of folds[29].

Fig. 3 .
Fig. 3. Submucosal layer "bundle" after removal of the lesion (type 0-IIIa according to the Paris classification, size 7 mm) with a cold loop.

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ESGE guidelines [13]indicate when advanced techniques for detecting or characterising epithelial lesions can be used during colonoscopy in patients with intermediate and high risk of CRC and when their use is mandatory: H i g h -r e s o l u t i o n e n d o s c o p y, d y e -s e n s i t i s e