Analysis of interobserver reproducibility in grading dysplastic nevi: Results of the application of the 2018 World Health Organization grading criteria

Background: We aimed to determine whether the histopathological grading of dysplastic nevi is an objective endeavor, considering interobserver variability, according to 2018 World Health Organization (WHO) criteria.

Methods: In total, 179 cases of dysplastic nevi, with high and moderate degree of atypia, diagnosed and graded according to the previous criteria were reviewed by three pathologists. Then, the observers graded the dysplastic nevi as low or high according to 2018 WHO criteria.

Results: Grading of dysplastic nevi was in complete agreement in 99 out of 179 cases across three observers with a fair level of overall interobserver agreement (multirater κ_free : 0.40). The observers showed moderate to good agreement for most of the architectural features, except for criteria regarding focal continuous basal proliferation of melanocytes, density of non-nested junctional melanocytes, and presence of dyscohesive nests of intraepidermal melanocytes, whereas fair agreement was achieved for the cytological criteria.

Conclusions: The 2018 WHO criteria for dysplastic nevus will ensure a common approach to the diagnosis and grading of dysplastic nevi. However, histopathological criteria, such as cytological features and focal continuous basal proliferation of melanocytes, should be improved so as to ensure a more accurate surgical approach and risk assessment.