OBJECTIVE
To characterize laterally spreading tumors (LST) of the rectum and colon measuring ≥20 mm and to evaluate the effectiveness of endoscopic biopsy in preoperative diagnosis of dysplasia grade and the presence of adenocarcinoma.
MATERIAL AND METHODS
A retrospective analysis was conducted on LSTs measuring ≥20 mm, removed en bloc using endoscopic submucosal dissection from 2021 to 2023. Dysplasia grade (low-grade dysplasia — LGD, high-grade dysplasia — HGD) and/or the presence and size of adenocarcinoma were assessed based on preoperative biopsy (the “preliminary” group) and final morphological examination (the “final” group).
RESULTS
The study included 153 LSTs with an average lesion size of 49.01±1.93 mm. Locations were as follows: rectum — 46.4%, left colon — 18.9%, right colon — 34.7%. According to the Paris classification: LST-G-H — 10.5%, LST-G-NM — 69.9%, LST-NG-FE — 5.9%, LST-NG-PD — 13.7%. Adenocarcinoma foci were identified in 22.2% of cases, more frequently in the non-granular LST group (p=0.0057). Risk factors for malignancy in LSTs included non-granular type, rectal localization, and lesion size ≥31 mm for the granular type. In 97% of cases, there was a single adenocarcinoma focus with an average size of 10.8±1.02 mm, with a tendency to be larger in the non-granular type group. Histological concordance did not depend on the average tumor size, macroscopic type, or localization. The sensitivity and specificity of preoperative biopsy in diagnosing high-grade dysplasia and adenocarcinoma were 17.5% and 8.8%, and 84.0% and 100%, respectively.
CONCLUSION
The main risk factors for the presence of adenocarcinoma are non-granular LST type, rectal localization, and LST size ≥31 mm for the granular type. Preoperative biopsy from large LSTs has low sensitivity and positive predictive value for detecting early cancer and high-grade dysplasia and should not be the basis for determining the method of endoscopic resection.