Histopathologic features of melanoma in difficult-to-diagnose lesions vary in accuracy and reproducibility, a recent study found. With the aim of measuring the accuracy of histopathologic features in difficult-to-diagnose melanocytic tumors and the interobserver agreement of those features, researchers conducted a case-control study of histopathologic features of melanoma in 100 such melanocytic neoplasms (40 melanomas and 60 nevi). Slides were blindly evaluated by 5 dermatopathologists. Frequencies, predictive values, and interobserver agreement were calculated. They found:

• 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.