Melanocytic lesions excised from the skin: what percentage are malignant?

We estimated the diagnostic skill of clinicians managing melanocytic skin naevi by measuring the percentage of malignant melanomas, premalignant and potentially malignant naevi, in 1896 excised melanocytic lesions submitted to a pathology service over 11 weeks. They comprised 8 per cent. The percentage increased with age: 4 per cent in the under-40s, 17 per cent in those aged 40-59, and 30 per cent in those over 60, (P < 0.001, sex-adjusted). Although the percentage was twice as high in males (11 per cent) as females (6 per cent), after adjustment for age the difference was not significant. Invasive melanomas, 3 per cent of the total, were similar: 1 per cent were from under-40s; 7 per cent from those aged 40-59 years; and 14 per cent from those over 60. They comprised 4 per cent of lesions from males and 2 per cent from females. These trends may indicate poor specificity of clinical diagnosis, notwithstanding other reasons for removal of naevi (cosmetic), particularly among patients under 40, and females.