Differential findings in patients with proximal and distal advanced adenomas

Aims It has been described that colon cancer exhibits different characteristics depending on whether it is located proximally or distally. However, differences based on location have been less studied in preneoplastic lesions. The aim of the study is to evaluate whether proximal and distal advanced adenomas (AA) present clinical, histological, morphological, or molecular differences.

Methods A retrospective observational study that evaluates colonoscopies performed at our center during the year 2022. We selected explorations where at least one advanced adenoma was resected. The study variables were subsequently compared based on their location proximal to the splenic flexure (right colon) or distal to it (left colon). Advanced adenomas were defined as those larger than 10 mm, with high-grade dysplasia (HGD), or intraepithelial carcinoma. Molecular differences were analyzed based on alterations in the DNA repair system, which was evaluated through immunohistochemistry techniques for MLH1, MSH2, MSH6 and PMS2 proteins.

Results Out of 4143 colonoscopies performed during the study period, at least one AA was resected in 228 colonoscopies (5.5%), of which 141 (61.8%) were distal. The patient´s mean age was 67.6±13.2 years, with a predominance of males (57.9%). When demographic variables were compared, no differences were found in age, gender, smoking, or non-steroidal anti-inflammatory drugs use. However, patients with proximal AA had a higher frequency of previous polyp history (14.2% vs. 40.2%, p<0.001) and previous AA history (5.7% vs. 26.4%, p<0.001). Regarding polyp characteristics, no differences were found in size, but morphological differences were observed, with sessile (34% vs. 60.9%) or flat polyps (2.1% vs. 17.2%, p<0.001) being more common in the right colon. Histologically, there were also differences, with a higher presence of HGD in the right colon (29.8% vs. 40.2%), but a higher percentage of intramucosal carcinoma in the distal location (13.5% vs. 2.3%, p=0.011). Finally, immunohistochemical analysis of DNA repair proteins showed nuclear positivity in all cases except for one proximal polyp [1] [2] [3].

Conclusions Mismatch repair status was not different between proximal and distal advanced adenomas. However, they exhibit different clinical, morphological, and histological characteristics which suggests that preneoplastic lesions may also have distinctive biological behaviors depending on their location.

 

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Conflicts of interest

Authors do not have any conflict of interest to disclose.

• References

• 1 Brueckl WM, Jung A, Wein A, Brabletz T, Guenther K, Nusko G. et al. Microsatellite instability in colorectal adenomas: relevance and clinical importance. Int J Colorectal Dis 2020; 15: 189-96
• 2 Weaver L, Boatman S, Kohn J, Mott SL, Gaertner WB, Madoff RD. et al. The role of tumor location on Endoscopic and surgical management of malignant colonic polyps. Ann Surg Oncol 2024; 31: 5452-6460
• 3 Wang H, Yuan Z, Wang S, Pang W, Wang W, Liu X. et al. The comparison of risk factors for colorectal neoplasms at different anatomical sites. Int J Colorectal Dis 2023; 38: 26

Publication History

Article published online:
27 March 2025