Seasonal pattern of the excision rate of melanoma and naevi

Based on available information that melanocytic skin lesions presenting a junctional component are more susceptible to the influence of ultraviolet radiation, this study compares the seasonal differences between the excision rates of melanocytic skin lesions with a junctional component to those without. The histological diagnoses of 1230 patients with melanocytic skin lesions were retrospectively analysed. Depending on the histological diagnosis four groups were formed: melanomas, dysplastic naevi, common naevi (junctional and compound naevi), and dermal naevi. All dates of operations were allocated to summer or winter halves of the year. The collected data were computer analysed for statistical description. The number of excisions of melanocytic lesions with a junctional component (melanoma, dysplastic naevi, common naevi) showed an impressive seasonal variation, with a peak during the summer months, while the excision frequency of dermal naevi was approximately constant during the year. In conclusion, we suggest that ultraviolet radiation may contribute to the seasonal pattern of excision of melanoma and naevi only when a junctional component is present.