Indexed on: 17 Jul '20Published on: 17 Jul '20Published in: Human Pathology
The diagnosis microscopic colitis (MC) relies on specific histopathological findings in colon biopsies. The number of biopsies needed to diagnose MC remains disputed. The aim of the study was to determine the number and site of biopsies necessary for the diagnosis and the effect of perpendicular orientation when embedding the biopsies. This retrospective multicenter European study included 42 patients with a consensus diagnose of collagenous colitis (CC), 51 with lymphocytic colitis (LC) and three with incomplete lymphocytic colitis (LCi). The number of individually diagnostic biopsies from each patient were determined. The diagnostic rate of 744 individual biopsies from 96 patients with MC was 69.5% for the specific MC subgroup, 79.4% for MC and 93.4% for MC plus incomplete MC (MCi). The risk of missing a diagnosis of the specific subgroup of MC when analyzing four biopsies was 0.87% decreasing to 0.18% for MC and 0.0019% for MC plus MCi. More biopsies from the right colon were diagnostic for the specific MC subgroup (76.3% vs. 64.0%, p=0.0014). Perpendicular orientation of biopsies increased the diagnostic rate for the specific MC subgroup (73.1% vs. 65.0%, p=0.0201). Histological changes diagnostic for MC were present in almost all biopsies with right colon and orientated biopsies more often being diagnostic for the specific MC subgroup. The results of this study indicate that four biopsies from the colon, rectum excluded, are sufficient to diagnose MC. Copyright © 2020 Elsevier Inc. All rights reserved.