A high incidence of melanoma found in patients with multiple dysplastic naevi by photographic surveillance

Objectives: (1) To assess the incidence of melanoma in a cohort of patients with dysplastic melanocytic naevi (DMN) and the relationships between incident melanomas and preexisting naevi and between melanoma risk and numbers of DMN. (2) To examine the role of the patient versus the physician in detecting melanoma and the relative value of surveillance versus prophylactic excision. Design: Prospective cohort study. Patients and setting: Two hundred and seventy-eight adults, each with five or more DMN, were followed up for a mean period of 42 months in a private dermatology practice. DMN were clinically diagnosed. Results: Twenty new melanomas were detected in 16 patients, corresponding to an age-adjusted incidence of 1835/100 000 person-years, 46 times the incidence in the general population. Eleven were detected because of changes evident in comparison with baseline photographs and nine were detected by patients or their partners. Thirteen of the 20 melanomas arose as new lesions and only three from DMN. Melanoma risk rose with increasing numbers of DMN. Conclusions: Increasing numbers of DMN are associated with increasing melanoma risk. Surveillance (baseline photography and follow-up) enabled early diagnosis of melanoma and was very much more cost-effective in preventing life-threatening melanoma than prophylactic excision of DMN.