[Flat, depressed and polypoid colorectal lesions: a comparative study using a index of histological advance]. / Lesiones planas, deprimidas y polipoides colorrectales: estudio comparativo utilizando un índice de avance histológico.

ABSTRACT

BACKGROUND: It has been described that the histological changes in flat and depressed colon lesions are more advanced than the ones in polypoid lesions. OBJECTIVES: To compare the histological findings in flat or depressed (non polypoid) and elevated (polypoid) colon lesions. To validate the use of a newly developed Histological Advance Index to compare results. MATERIALS & METHODS: Prospective observational study. Population in study consisted of adult patients programmed for an elective colonoscopy at a private endoscopy center in Lima- Perú. Two groups 417 found to have non polypoid lesions (which included flat, depressed and lateral spreading tumors or LST), and 405 with polypoid lesions. RESULTS: Total of 8,248 patients, with 417(5%) in the non polypoid group; 368(4.5%) in the flat lesion group, 27(0.32%) in the depressed and 22 (0.26%) LSTs. According to our index, flat and polypoid lesions showed no difference in histological findings. LSTs had a more advanced histology and depressed lesions reached the highest index scores. Flat lesions were found more often in right colon compared with polypoid ones (31% vs 22%, p<0.01), with a higher percentage of serrated lesions (9% vs 2%, p<0.01) and high grade dysplasia (5% vs 3%, NS). In contrast, depressed lesions, showed high grade dysplasia in 3.7% (NS) but cancer in 18% (p<0.01) LSTs were found mainly in right colon and rectum, showing villous component in 23%(p< 0.01) and high grade dysplasia in 32%(p <0.01), but no cancer was found. CONCLUSIONS: Flat and polypoid lesions showed similar histological findings, but LSTs were found to have a higher prevalence of villous lesions and high grade dysplasia. Depressed lesions were found to have a higher prevalence of malignancy. Histological Advance Index proved to be a useful tool to compare groups and quantify differences. .