The presenting features of melanoma in New Zealand: implications for earlier detection

Objective: To examine the relationship between presenting features and histological characteristics of melanomas in New Zealand. Methods: Cases were participants in a national melanoma case-control study. Histological data were extracted from a Cancer Registry download. Associations between categorical variables were assessed using the χ² test; linear regression was used for continuous variables and multinomial logistic regression for non-binary categorical dependent variables. Results: Most melanomas were self-detected. Lesions >2mm depth took longer to diagnose, predominantly due to patient delay. The commonest presenting feature was colour. After adjustment for depth, nodular melanomas were less likely than superficial spreading melanomas to present because of shape or colour, but more likely to be raised. After adjustment for subtype, thick melanomas were significantly more likely to be bigger, raised, bleeding or crusting, and inflamed, itchy or sore. Conclusions: Nodular and thick melanomas failed to fulfil the ABCDE criteria: the ‘A’, ‘B’ and ‘C’ discriminated poorly; and ‘D’ for diameter may exclude small but thick lesions. The ‘E’ criterion (elevation/enlargement/evolution) was perhaps best for detecting these melanomas. Implications for public health: Public education for earlier diagnosis in New Zealand needs to include the presenting features of nodular and thick melanomas and to strongly encourage seeking early physician advice.