Histopathologic features of melanoma in difficult-to-diagnose lesions: A case-control study

Abstract

Background: Dermatopathology is considered the gold standard for melanoma diagnosis, but a subset of cases is difficult to diagnose by histopathology.

Objective: The goals of this study were to measure the accuracy of histopathologic features in difficult-to-diagnose melanocytic tumors and the interobserver agreement of those features.

Methods: This is a case-control study of histopathologic features of melanoma in 100 difficult-to-diagnose melanocytic neoplasms (40 melanomas and 60 nevi). Slides were blindly evaluated by 5 dermatopathologists. Frequencies, predictive values, and interobserver agreement were calculated. Univariate and multivariate logistic regression analyses were performed to identify the most influential features in arriving at a diagnosis of melanoma.

Results: Asymmetry, single-cell melanocytosis, solar elastosis, pagetoid melanocytosis, and broad surface diameter were most influential in arriving at a diagnosis of melanoma. Asymmetry and single-cell melanocytosis were most predictive of melanoma. Fleiss kappa was <0.6 for interobserver agreement in 9/10 histopathologic features of melanoma.

Limitations: This study is limited by the small sample size, selection bias, and binary classification of melanocytic lesions.

Conclusion: Our results indicate histopathologic features of melanoma in difficult-to-diagnose lesions vary in accuracy and reproducibility.

Keywords: atypical nevus; diagnostic agreement; histopathology; melanoma.