Reproducibility of the Villous Component and High-grade Dysplasia in Colorectal Adenomas <1 cm

The presence of high-grade dysplasia (HGD) or villous component (VC) defines an advanced adenoma (AA) in patients with 1 or 2 adenomas <1 cm in size. Current consensus guidelines recommend that patients with AA undergo more intense postpolypectomy surveillance. In these clinical situations, the interobserver reliability in determining VC and HGD would play a major role in the credibility of these consensus guidelines. Therefore, the purpose of this study was to evaluate interobserver variability of VC and HGD in polyps <1 cm before and after the development of consensus criteria among gastrointestinal (GI) pathologists. Five GI pathologists independently evaluated 107 colorectal adenomas <1 cm, and classified them into tubular adenomas or adenomas with a VC (A-VC) and into low-grade dysplasia or HGD. Then a consensus conference was held and consensus criteria for VC and HGD were developed by group review. The same set of 107 slides were rereviewed independently by the same 5 GI pathologists. Interobserver variability using κ statistical analysis before and after the application of consensus criteria was assessed. A 1-sided z-test was used to determine whether κ scores increased after the consensus conference. Interobserver agreement before and after the consensus conference was poor for assessment of A-VC, HGD, and AA. These data calls into question the validity of basing clinical decisions on this distinction.