ABCDE Melanoma Rule

An unfamiliar or changing pigmented lesion is a finding to triage, not a bedside diagnosis. The ABCDE rule organizes visual clues that increase concern for melanoma: asymmetry, an irregular border, colour variation, a larger diameter, and evolution over time. It is a case-finding aid that should lead to clinician assessment, not a reason to label a lesion benign or to observe it indefinitely. The rule has two important limits. A lesion smaller than 6 mm may still be melanoma, and some melanomas are amelanotic or occur in locations where the classic pattern is unreliable. A complete skin assessment therefore includes the scalp, mucosal-adjacent areas when indicated, palms, soles, interdigital spaces and nail units in patients of every skin tone. A new dark streak beneath a nail or an unusual lesion on the sole deserves attention even if it is symmetrical and uniformly coloured. Canada has no current national recommendation for population-wide visual skin examination of asymptomatic people. That does not change the response to a suspicious or changing lesion, nor does it remove the need for periodic complete examinations in...