Melanocytic naevus or malignant melanoma? A large-scale epidemiological study of diagnostic accuracy.

While the early detection of malignant melanoma is important and has been emphasized widely in the past few years, it is difficult to accomplish. The purpose of this study is to assess how well dermatologists recognize malignant melanomas in patients with naevi. Information from 9,121 patients visiting two dermatological clinics in Stockholm and diagnosed melanocytic naevi was linked with the Swedish Cancer Registry to identify individuals with records of malignant melanoma. One-hundred-and-thirteen cases of malignant melanoma were detected in the study population. Sixty patients were diagnosed malignant melanoma prior to the naevus diagnosis and most of them were under continuous follow-up. A further 35 patients were diagnosed malignant melanoma and naevus at the same time. The remaining 18 were given the diagnoses malignant melanoma after the naevus diagnosis and, of these, 6 cases were detected more than 6 years after examination and malignant melanoma was considered not present at the time of consultation. Three cases can be considered as missed (6%) and four others as partially missed or delayed. Thus, of 47 cases of probable recognizable malignant melanoma, there was insufficient management of 7 (15%). Six cases were detected during dermatological examination for other conditions and five through general examination of naevi. Although a few possibly detectable malignant melanomas were not discovered, the results of this study reflect a high clinical detection rate. In addition, a number of cases were discovered by chance during examinations for other dermatological conditions.