**4. Prognostic factors**

Many factors have been associated with a higher probability of residual disease or recurrent carcinoma.

#### **4.1. Morphology**

Only 5% of adenomas are in danger of becoming malignant. The probability of high grade dysplasia and carcinomatous transformation increases with polyp size, a villous component, when there are many polyps or the age at diagnosis is more than 60 years [2]. The neoplasia is considered to be advanced when polyp size is 1 cm or more, there is a villous component or a high degree of dysplasia. Mixed polyps also have the ability to become malignant, as does hyperplastic polyposis syndrome. More than 25% of advanced polyps are located in

The prevalence of cancerous polyps in series of endoscopically removed polyps is between 0.2% and 11% [4-6].Currently, screening programs allow the detection and treatment of a great number of adenomas and malignant polyps, and this contributes to a reduction of the mortality by colorectal cancer (CRC) [1,7]. In an asymptomatic population of people over 50 years old who underwent direct colonoscopy, there was a 0.8% prevalence of adenocarcino‐ ma of which 50% were carcinoma "in situ" or in stage I [8,9]. During screening programmes, adenocarcinomas have been detected in between 3% - 4.6% of those who undergo colono‐

Carcinoma "in situ", intramucosal carcinoma, high displasia or intraepithelial carcinoma is the stage at which there is no involvement of *the muscularis mucosa.* In general, this tumour stage does not cause metastasis. It is classified as pTis or Stage 0 in the TNM staging system.These terms are defined as non-invasive high grade neoplasia in the Vienna classification [12].Carci‐ noma in situ or severe displasia or intraepithelial carcinoma corresponds to a carcinoma that is restricted to the epithelial layer without invasion into the lamina propria. Intramucosal car‐

When the carcinoma spreads to the submucosa, the polyp is considered to have become ma‐ lignant, being able to spread to lymph nodes or distant sites. The tumours that affect the submucosa are classified as T1 and correspond to Stage I of the TNM staging system. This

The term pseudoinvasion refers to the presence of glandular epithelium of the mucosa be‐ neath the muscularis mucosa in colonic polyps. These lesions have no malignant potential and should be management in a similar way to adenomas [13]. However, an inexperienced pathologist can mistake this phenomenon for invasive carcinoma. Pseudoinvasion usually occurs in large polyps (>1 cm), especially those with long stalks, and is most commonly found in polyps of the sigmoid colon. Islands of adenomatous epithelium are displaced through the muscularis mucosa and are found within the submucosa of the stalk. The dis‐ placed glandular tissue usually has rounded not infiltrative, contours, carries with it a small

scopy following a positive immunological faecal occult blood test result [10,11].

cinoma is a carcinoma characterized by the invasion into the lamina propria.

term is defined as submucosal carcinoma in the classification of Vienna [12].

the area proximal to the splenic flexure [3].

124 Colonoscopy and Colorectal Cancer Screening - Future Directions

**2. Epidemiology**

**3. Histology**

Morphology is described as polypoid (pedunculated or sessil) and nonpolypoid (flat or ul‐ cerated) subtypes according to the Paris classification [17]. The type of polyp and its mor‐ phology can guide the endoscopist towards its potential malignancy [2,18,19]. These features include the size, the presence of depressed ulceration, irregular contours, deformi‐ ty, a short and immobile stalk and the inability to elevate a sessile polyp when a submucosal bleb is formed. In such suspicious lesions, as well as in flat or depressed lesions, diagnosis can be carried out using chromoendoscopy and magnification techniques that can highlight abnormalities of glandular cytoarchitecture and reveal information concerning the extent of submucosal invasion [20,21].

Kudo et al. [22] developed the pit pattern classification for colon polyps with six classes of surface pattern depicted by magnifying endoscopy after indigo carmine staining. Class 5 of this pit-pattern classification or an unstructured surface has been shown to correlate well with a diagnosis of malignancy, and can provide important additional information prior to endoscopic treatment. However, endoscopic ultrasound using high frequency transendosco‐ picminiprobes currently appears to be the most accurate method for defining submucosal or further bowel wall invasion, enabling direct referral for surgical intervention in those cases

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The success of treatment of a malignant polyp depends on the complete resection by poly‐ pectomy or surgical intervention. When en-bloc removal of a polyp is performed, it is possi‐ ble to assess the depth of infiltration of the tumour cells and whether the margin is affected. Pedunculated malignant polyps are easily removed using a loop snare. However, this tech‐ nique frequently results in piecemeal removal when applied to sessile and flat malignant polyps. Nevertheless, around one-third of malignant polyps are removed in this way [24]. En-bloc removal is advantageous because it allows full histological evaluation of the com‐ plete resection and is associated with lower recurrence rates than piecemeal removal [25]. Endoscopic submucosal dissection (ESD) has been found to be particularly useful for the re‐ moval of sessile or flat adenomatous lesions. It has an advantage over other endoscopic techniques in that it allows en-bloc removal of large (>2 cm) colonic lesions. In ESD an elec‐ trosurgical cutting device is used to carefully dissect the deeper layers of the submucosa to remove neoplastic lesions in the mucosa. In a meta-analysis it was found that ESD en-bloc resection is achieved in 84.9% of lesions, and clear vertical and lateral margins are achieved

**4.3. Level of invasion of adenocarcinoma into the polyp and polypectomy resection**

Properly marked and orientated specimens are essential.

Haggitt et al. [27] have assigned levels of invasion to each malignant polyp. In this study, level 1 described invasive adenocarcinoma limited to the polyp head, level 2 included in‐ volvement of the neck, level 3 corresponded to adenocarcinoma cells in the stalk, and level 4 to invasion, adenocarcinoma cells infiltrating the submucosa at the level of the adjacent bowel wall. In this system, invasive adenocarcinoma in a sessile polyp by definition had lev‐ el 4 invasion. However, precise histological evaluation of Haggitt's level may be difficult.

More recently, some authors have proposed an additional histological classification system based on the grade of cell differentiation at the lesion margins and on the size and depth of invasion of the submucosa. Submucosal invasion has been classified into three types based on the depth of invasion. When less than one-third of the submucosa is invaded the stage is sm1, and if more than two-thirds is invaded the stage is sm3, while stage sm2 is intermedi‐ ate with invasion of cancer into the middle third. It has been shown that penetration of can‐ cerous cells is associated with a risk of lymphatic spread [29-32]. Research based on large

with deeper infiltration who are at the greatest risk of lymphatic spread [23].

**4.2. Type of resection**

in 75.3% of cases [26].

**margin**

**Table 1.** The Paris Endoscopy Classification of superficial neoplastic lesions [17]

**Figure 2.** Polyps in colon: Pedunculated polyp 0‐Ip (A), sessile polyp 0‐Is (B y C), flat polyp 0‐IIb (D y F), superficial **Figure 2.** Polyps in colon: Pedunculated polyp 0-Ip (A), sessile polyp 0-Is (B y C), flat polyp 0-IIb (D y F), superficial ele‐ vated with central depression 0-IIa + IIc (E) and excavated polyp 0-IIc (G y H).

elevated with central depression 0‐IIa + IIc (E) and

excavated polyp 0‐IIc (G y H).

Kudo et al. [22] developed the pit pattern classification for colon polyps with six classes of surface pattern depicted by magnifying endoscopy after indigo carmine staining. Class 5 of this pit-pattern classification or an unstructured surface has been shown to correlate well with a diagnosis of malignancy, and can provide important additional information prior to endoscopic treatment. However, endoscopic ultrasound using high frequency transendosco‐ picminiprobes currently appears to be the most accurate method for defining submucosal or further bowel wall invasion, enabling direct referral for surgical intervention in those cases with deeper infiltration who are at the greatest risk of lymphatic spread [23].

#### **4.2. Type of resection**

**TIPO O**

**POLYPOID NON POLYPOID**

Slightly Elevated

Protruded, pedunculated Protruded, sessile

126 Colonoscopy and Colorectal Cancer Screening - Future Directions

**Table 1.** The Paris Endoscopy Classification of superficial neoplastic lesions [17]

A B

C D

E F

G H

excavated polyp 0‐IIc (G y H).

vated with central depression 0-IIa + IIc (E) and excavated polyp 0-IIc (G y H).

**Figure 2.** Polyps in colon: Pedunculated polyp 0‐Ip (A), sessile polyp 0‐Is (B y C), flat polyp 0‐IIb (D y F), superficial elevated with central depression 0‐IIa + IIc (E) and

**Figure 2.** Polyps in colon: Pedunculated polyp 0-Ip (A), sessile polyp 0-Is (B y C), flat polyp 0-IIb (D y F), superficial ele‐

0-Ip 0-Is 0-IIa 0-IIb 0-IIc 0-III

Flat Slightly

Depressed

Excavated (ulcer)

The success of treatment of a malignant polyp depends on the complete resection by poly‐ pectomy or surgical intervention. When en-bloc removal of a polyp is performed, it is possi‐ ble to assess the depth of infiltration of the tumour cells and whether the margin is affected. Pedunculated malignant polyps are easily removed using a loop snare. However, this tech‐ nique frequently results in piecemeal removal when applied to sessile and flat malignant polyps. Nevertheless, around one-third of malignant polyps are removed in this way [24]. En-bloc removal is advantageous because it allows full histological evaluation of the com‐ plete resection and is associated with lower recurrence rates than piecemeal removal [25]. Endoscopic submucosal dissection (ESD) has been found to be particularly useful for the re‐ moval of sessile or flat adenomatous lesions. It has an advantage over other endoscopic techniques in that it allows en-bloc removal of large (>2 cm) colonic lesions. In ESD an elec‐ trosurgical cutting device is used to carefully dissect the deeper layers of the submucosa to remove neoplastic lesions in the mucosa. In a meta-analysis it was found that ESD en-bloc resection is achieved in 84.9% of lesions, and clear vertical and lateral margins are achieved in 75.3% of cases [26].

#### **4.3. Level of invasion of adenocarcinoma into the polyp and polypectomy resection margin**

Haggitt et al. [27] have assigned levels of invasion to each malignant polyp. In this study, level 1 described invasive adenocarcinoma limited to the polyp head, level 2 included in‐ volvement of the neck, level 3 corresponded to adenocarcinoma cells in the stalk, and level 4 to invasion, adenocarcinoma cells infiltrating the submucosa at the level of the adjacent bowel wall. In this system, invasive adenocarcinoma in a sessile polyp by definition had lev‐ el 4 invasion. However, precise histological evaluation of Haggitt's level may be difficult. Properly marked and orientated specimens are essential.

More recently, some authors have proposed an additional histological classification system based on the grade of cell differentiation at the lesion margins and on the size and depth of invasion of the submucosa. Submucosal invasion has been classified into three types based on the depth of invasion. When less than one-third of the submucosa is invaded the stage is sm1, and if more than two-thirds is invaded the stage is sm3, while stage sm2 is intermedi‐ ate with invasion of cancer into the middle third. It has been shown that penetration of can‐ cerous cells is associated with a risk of lymphatic spread [29-32]. Research based on large patient series has shown a 1-3% risk for lymph node metastases in sm1 cancers, 8% in sm2 cancers and 23% in sm3 cancers [29].

**4.4. Stage of differentiation**

Four grades were considered [32]:

cases is of the order of 36-38% [30].

**4.5. Lymphatic invasion**

Grade 1: Corresponded to a well-differentiated intestinal-type adenocarcinoma with well-

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Grade 2: Moderately differentiated intestinal-type adenocarcinoma containing solid nests

Grade 3: Carcinoma is poorly differentiated intestinal–type. Signet ring cell or mucinous ad‐ enocarcinoma, composed of hyperchromatic cells arranged into solid sheets and forming ab‐

Grade 4: Undifferentiated tumours which have less than 5% glandular differentiation.

Undifferentiated carcinoma: Medullary carcinomas with high microsatellite instability.

The prognosis correlates with the histological grade [32]. For example, Grade 3 of differen‐ tiation is seen in 5.7 to 9.2% of patients and the risk of residual lesions or relapse in these

Lymphatic invasion is defined as tumour cells within a true endothelial-lined channel in the absence of red blood cells [33]. The risk of lymphatic spread has been estimated by histologi‐ cal study of resected specimens. Since lymphatics do not penetrate much beyond the muscu‐ laris mucosae, focal cancer that has not invaded through this layer appears to present little or no risk of lymph node spread [34]. The near absence of lymphatics within the mucosa has been proposed as the reason for the observed lack of malignant potential (lymph node meta‐ stasis) observed in polyps showing only intramucosal carcinoma. However, this theory has been challenged by studies using more sensitive techniques to detect lymphatic vessels. Studies using the relatively new antibody D2-40, which stains lymphatic but not blood ves‐ sel endothelium, have shown that lymphatic present in the stalk and mucosa of adenomas and undergo proliferation, are early invasive cancers. Lymphatic channels are often present

Detecting lymphatic invasion by expert pathologists using light microscopy is difficult. There are no recognized guidelines for establishing the presence of lymphatic invasion (for example, the number of sections or immunostains needed to identify lymphatic vessels). For example, in a study in which five pathologists assessed the lymphatic invasion of 140 malig‐ nant polyps, they agreed (4 out of 5 observers) on only 17 cases [37].The intra and inter-ob‐ server variability in the interpretation of samples received among even the most expert histopathologists can be high and often leads to diagnostic uncertainties [37]. The use of im‐ munohistochemistry for D2-40 may help identify lymphatic channels. However, its use is not yet routine, and technical issues such as loss of a suspicious focus in level sections limits the usefulness of special stains in this setting. The presence of lymphatic invasion has been proposed by some researchers as an indication for colectomy. However, few malignant pol‐

formed glands and open lumina or with more than 95% glandular differentiation.

showing only focal glands or with 50-95% glandular differentiation.

sorptive glands, with 5% to 50% glandular differentiation.

near nests of infiltrating tumours in malignant polyps [35,36].

**Figure 3.** Resection of a pedunculated polyp with an endoscopic **Figure 3.** Resection of a pedunculated polyp with an endoscopic snare (A-D).

snare (A‐D).

snare (A‐D). In sessile polyps, it is essential that the pathologist identifies the stalk or the depth of the diathermy burn. The risk of relapse ranges from 0% to 2% in malignant polyps with a mar‐ gin of resection greater than 1 mm. If the resection margin is involved, or is less than 1 mm, the percentage of relapse ranges between 21% and 33% [30]. Most authors believe that a re‐ section margin of more than 1 mm is safe and that in such cases the probability of residual disease or recurrent carcinoma is low [4,5,30,31]. **Figure 3.** Resection of a pedunculated polyp with an endoscopic

**Figure 4.** Elevation of a superficial elevated polyp (0‐IIb) with Indigo Carmine **Figure 4.** Elevation of a superficial elevated polyp (0-IIb) with Indigo Carmine

#### **4.4. Stage of differentiation**

patient series has shown a 1-3% risk for lymph node metastases in sm1 cancers, 8% in sm2

**Figure 3.** Resection of a pedunculated polyp with an endoscopic

In sessile polyps, it is essential that the pathologist identifies the stalk or the depth of the diathermy burn. The risk of relapse ranges from 0% to 2% in malignant polyps with a mar‐ gin of resection greater than 1 mm. If the resection margin is involved, or is less than 1 mm, the percentage of relapse ranges between 21% and 33% [30]. Most authors believe that a re‐ section margin of more than 1 mm is safe and that in such cases the probability of residual

**Figure 3.** Resection of a pedunculated polyp with an endoscopic

**Figure 4.** Elevation of a superficial elevated polyp (0‐IIb) with Indigo

**Figure 4.** Elevation of a superficial elevated polyp (0‐IIb) with Indigo

cancers and 23% in sm3 cancers [29].

128 Colonoscopy and Colorectal Cancer Screening - Future Directions

snare (A‐D).

disease or recurrent carcinoma is low [4,5,30,31].

Carmine

snare (A‐D).

A B

C D

A B

**Figure 3.** Resection of a pedunculated polyp with an endoscopic snare (A-D).

Carmine **Figure 4.** Elevation of a superficial elevated polyp (0-IIb) with Indigo Carmine

C D

Four grades were considered [32]:

Grade 1: Corresponded to a well-differentiated intestinal-type adenocarcinoma with wellformed glands and open lumina or with more than 95% glandular differentiation.

Grade 2: Moderately differentiated intestinal-type adenocarcinoma containing solid nests showing only focal glands or with 50-95% glandular differentiation.

Grade 3: Carcinoma is poorly differentiated intestinal–type. Signet ring cell or mucinous ad‐ enocarcinoma, composed of hyperchromatic cells arranged into solid sheets and forming ab‐ sorptive glands, with 5% to 50% glandular differentiation.

Grade 4: Undifferentiated tumours which have less than 5% glandular differentiation.

Undifferentiated carcinoma: Medullary carcinomas with high microsatellite instability.

The prognosis correlates with the histological grade [32]. For example, Grade 3 of differen‐ tiation is seen in 5.7 to 9.2% of patients and the risk of residual lesions or relapse in these cases is of the order of 36-38% [30].

#### **4.5. Lymphatic invasion**

Lymphatic invasion is defined as tumour cells within a true endothelial-lined channel in the absence of red blood cells [33]. The risk of lymphatic spread has been estimated by histologi‐ cal study of resected specimens. Since lymphatics do not penetrate much beyond the muscu‐ laris mucosae, focal cancer that has not invaded through this layer appears to present little or no risk of lymph node spread [34]. The near absence of lymphatics within the mucosa has been proposed as the reason for the observed lack of malignant potential (lymph node meta‐ stasis) observed in polyps showing only intramucosal carcinoma. However, this theory has been challenged by studies using more sensitive techniques to detect lymphatic vessels. Studies using the relatively new antibody D2-40, which stains lymphatic but not blood ves‐ sel endothelium, have shown that lymphatic present in the stalk and mucosa of adenomas and undergo proliferation, are early invasive cancers. Lymphatic channels are often present near nests of infiltrating tumours in malignant polyps [35,36].

Detecting lymphatic invasion by expert pathologists using light microscopy is difficult. There are no recognized guidelines for establishing the presence of lymphatic invasion (for example, the number of sections or immunostains needed to identify lymphatic vessels). For example, in a study in which five pathologists assessed the lymphatic invasion of 140 malig‐ nant polyps, they agreed (4 out of 5 observers) on only 17 cases [37].The intra and inter-ob‐ server variability in the interpretation of samples received among even the most expert histopathologists can be high and often leads to diagnostic uncertainties [37]. The use of im‐ munohistochemistry for D2-40 may help identify lymphatic channels. However, its use is not yet routine, and technical issues such as loss of a suspicious focus in level sections limits the usefulness of special stains in this setting. The presence of lymphatic invasion has been proposed by some researchers as an indication for colectomy. However, few malignant pol‐ yps with lymphatic invasion have been reported, and most of them have had positive mar‐ gins, grade 3 invasive adenocarcinoma (as defined above), or both [5].

nant should also be tattooed. Among the criteria that should hint the endoscopist about the presence of malignancy in the polyps is size, an irregular surface or a flat or excavated mor‐

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The size of the polyp is an important factor that indicates malignancy [42,44-46]. The proba‐ bility of dysplasia could be up to 38,5% in those larger than 1 cm [47].The flat or ulcerated lesions have a higher risk of high-grade dysplasia or carcinoma [22,48-50]. The probability of cancer or severe dysplasia increases from 4% in small flat lesions, up to 6% in small polyps, 16% in large polyps and 29% in long, flat lesions, and up to 75% in depressed lesions [51].

However, tattooing in suspicious polyps at first colonoscopy, in our experience is still low, 17.6%. We study a retrospective series that include 74 patients. Our endoscopists usually marked large polyps, polyps resected in a fragmented manner and polyps with proximal lo‐ cation. However, in a multivariate analysis only proximal location was significant associated with marking. It is known that flat polyps, with a greater potential for malignancy, are most frequently located in the right colon [37,39]. In our series, 16.2% of the polyps were proxi‐ mal; of these, 58.3% were marked; on the other hand, only 9.7% of the distal polyps were marked. The factors that could have a greater influence when it comes to marking proximal polyps more frequently was their potential to become malignant in this location and the dif‐

We agree with other authors [52-57] that tattooing is one of the best methods for tumor location, either if the patient is following-up by colonoscopy or is undergoing for surgical

Prior to removal of the polyp, it is difficult to know whether the polyp is malignant or not. Some features, as we have mentioned earlier, can give some indication of the degree of ma‐ lignancy. Regardless of the morphological characteristics, a polyp is normally removed

Polypectomy should be performed en bloc, since this is essential to establish and define fa‐ vourable or unfavourable histological criteria. In just a few cases, only polyp biopsies are performed, such a lack of coagulation data, polyp could be difficult to remove at that point

The indication for a malignant polyp with sessile morphology, regardless of favourable his‐ tological criteria, is surgery [10], especially in patients younger than 50 years old, who tend to present fewer surgical complications [59]. Surgical treatment is recommended for malig‐ nant polyps with pedunculated morphology which have unfavourable histological criteria (partial polyp resection, poorly differentiated carcinoma, vascular or lymphatic invasion, or lesions ≤1 mm from the polypectomy) [10]. On the other hand, for malignant polyps with pedunculated morphology but with favourable histological criteria, polypectomy is consid‐ ered to be curative (Figure 7). Non-invasive high grade neoplasia regardless of their mor‐

ficulty of finding the polypectomy scar in subsequent controls or in surgery.

in time, or the patient being on antiplatelet drugs or anticoagulants.

phology [2,18,42,43].

resection [42,58].

**5. Treatment**

when detected.

#### **4.6. Vascular invasion**

The presence of vascular invasion is defined as cancer in an endothelial-lined channel sur‐ rounded by a smooth muscle wall [35]. However, it is difficult to recognise it. Vascular markers (CD31, CD34 and factor VIII) may help. These markers strongly stain blood vessel endothelium, and to a lesser extent lymphatic endothelium [14].The prevalence of venous invasion in malignant polyps varies greatly, ranging from 3.5% to 39% [37].Often venous in‐ vasion is associated with lymphatic invasion and/or tumours which have a resection margin of less than 2 mm and/or are poorly differentiated. In contrast, Talbot et al. [38] observed that venous invasion was not associated with poorer prognosis.

#### **4.7. Risk of residual disease or recurrent carcinoma in favourable and unfavourable histology**

Favourable histology is defined as grade 1 or 2 differentiated adenocarcinoma in which car‐ cinoma cells are at least 1 mm from a clearly visualized margin, resection is carried out en bloc and there is an absence of vascular or lymphatic invasion.

Unfavourable histology is defined as polyps with biopsy margin ≤1 mm, tumour within the cauterized region constitutes a positive margin, piecemeal removal, poorly differentiated tu‐ mour (grade 3) or lymphatic or vascular invasion.In these cases, surgical resection is indicat‐ ed because of the increased risk of lymph node metastasis or residual disease [14]. On the other hand, in the absence of unfavourable features, polypectomy is considered curative. Sometimes, specimens do not lend themselves to proper analysis for any reason (piecemeal removal or poor orientation) result in a default decision to resect.

In 1995, Volk et al [5] reviewed 20 studies in which 858 malignant polyps were analysed. They observed residual disease or recurrent carcinoma in 89 patients (10%). However, there were relapses or tumours in the area of the resection in only 8 (1%) patients with favourable histological criteria. Subsequent studies have also reported an incidence of less than 1% [37,39]. Only one study described incidence higher than 5% in malignant polyps with fa‐ vourable histology [40] and the study itself has been widely criticized from subsequent re‐ views [5]. By contrast, in malignant polyps with unfavourable histology, the risk of relapse or residual lesions ranges between 10% and 39% [5,14,29,39].

#### **4.8. Marking with India Ink**

In 1975, Ponsky and King [41] published the first case in which marking with India ink was used with the purpose of locating the polyp during the surgical procedure. Sometimes to lo‐ cate the base of the polyp after polypectomy or during surgery is extremely difficult.

All the endoscopicallyunresectable polyps in patients in whom surgery would be consid‐ ered, should be tattooed. Endoscopicallyresectable polyps that could have become malig‐ nant should also be tattooed. Among the criteria that should hint the endoscopist about the presence of malignancy in the polyps is size, an irregular surface or a flat or excavated mor‐ phology [2,18,42,43].

The size of the polyp is an important factor that indicates malignancy [42,44-46]. The proba‐ bility of dysplasia could be up to 38,5% in those larger than 1 cm [47].The flat or ulcerated lesions have a higher risk of high-grade dysplasia or carcinoma [22,48-50]. The probability of cancer or severe dysplasia increases from 4% in small flat lesions, up to 6% in small polyps, 16% in large polyps and 29% in long, flat lesions, and up to 75% in depressed lesions [51].

However, tattooing in suspicious polyps at first colonoscopy, in our experience is still low, 17.6%. We study a retrospective series that include 74 patients. Our endoscopists usually marked large polyps, polyps resected in a fragmented manner and polyps with proximal lo‐ cation. However, in a multivariate analysis only proximal location was significant associated with marking. It is known that flat polyps, with a greater potential for malignancy, are most frequently located in the right colon [37,39]. In our series, 16.2% of the polyps were proxi‐ mal; of these, 58.3% were marked; on the other hand, only 9.7% of the distal polyps were marked. The factors that could have a greater influence when it comes to marking proximal polyps more frequently was their potential to become malignant in this location and the dif‐ ficulty of finding the polypectomy scar in subsequent controls or in surgery.

We agree with other authors [52-57] that tattooing is one of the best methods for tumor location, either if the patient is following-up by colonoscopy or is undergoing for surgical resection [42,58].
