Age-related prevalence of dermoscopy patterns in acquired melanocytic naevi.

Background: Based on the dermoscopic classification of acquired melanocytic naevi, six different dermoscopic types can be distinguished by morphology (globular, globular-reticular, globular-homogeneous, reticular, reticular-homogeneous, homogeneous) and by pigment distribution (uniform, central hyperpigmentation, central hypopigmentation, peripheral hyperpigmentation, peripheral hypopigmentation, multifocal hyper/hypopigmentation). It has been suggested that most individuals harbour one predominant dermoscopic type among their naevi.

Objectives: To evaluate whether the age of the patient influences the predominant naevus pattern observed in individuals with multiple acquired melanocytic naevi.

Methods: Individuals were recruited from the pigmented skin lesion clinic in Graz between July 2000 and February 2001. Individuals with at least 10 melanocytic naevi were selected consecutively until a total of 10 individuals in each of five age groups was obtained. Age groups were: 0-15 years, 16-30 years, 31-45 years, 46-60 years and > 60 years. Digitized images of acquired melanocytic naevi, defined as benign melanocytic proliferations having a diameter of at least 5 mm with a macular component and which were not apparent within the first year of life, were evaluated by dermoscopic criteria. The associations of dermoscopic features as a function of patient age were analysed. We calculated absolute numbers and frequencies, given as percentages, as well as predominance of the dermoscopic types of naevi in the different age groups.

Results: Analysis of 1268 naevi revealed that the globular pattern predominated in the youngest age group. By contrast, the reticular and/or homogeneous patterns were increasingly exhibited in naevi from older individuals (older than 15 years). Uniform pigmentation was most common in melanocytic naevi in the youngest age group, while central hyperpigmentation was predominantly seen in the group of individuals aged 16-30 years.

Conclusions: The predominance of dermoscopic types of melanocytic naevi varies according to the individual's age. Awareness of the age-related dermoscopic predominance of melanocytic naevi might allow more accurate recognition of dermoscopic patterns of melanocytic skin lesions that are unusual with respect to the individual's age. This observation may help in the early recognition of some 'banal'-appearing melanomas. Furthermore, the observations made in this study raise interesting questions regarding naevus evolution.