Assessing the reproducibility of the microscopic diagnosis of sessile serrated adenoma of the colon.

INTRODUCTION: sessile serrated adenoma (SSA) is a recently described lesion that may be related to the development of up to 15% of colorectal cancers (CRCs).

OBJECTIVE: to determine the accuracy of morphological criteria for the diagnosis of SSA by assessing concordance between pathologists.

MATERIAL AND METHODS: concordance between two pathologists in the diagnosis of serrated lesions of the colon was studied for 195 lesions (187 hyperplastic polyps and 7 serrated adenomas). Size, location, morphology, and sampling method were collected of each lesion. Both pathologists were unaware of the previous diagnosis, macroscopic characteristics, and location of lesions. Possible diagnoses were: SSA, traditional serrated adenoma (TSA), hyperplastic polyp (HP), serrated polyp, tubular adenoma, or mixed lesions. Diagnostic doubts had to be described. Concordance between both observers was assessed using the kappa index (ê). The influence of collected variables on concordance degree was also evaluated.

RESULTS: overall agreement on the histological diagnosis was poor (ê = 0.14), and so was agreement on the diagnosis of SSA (ê = 0.23). Concordance in the diagnosis of SSA improved with size > 5 mm (ê = 0.64) and proximal location (ê = 0.43).

CONCLUSION: in a real clinical setting, the existing morphological criteria for SSA identification may be difficult to use.