Frequency, clinical and dermoscopic features of benign papillomatous melanocytic naevi (Unna type)

Most previous studies on melanocytic naevi have not distinguished between the different types of naevi, except for some studies trying to define atypical naevi. No large, population-based studies on papillomatous or Unna-type melanocytic naevi have been performed.

To investigate the dermoscopic and clinical features of papillomatous naevi and to study some of the factors which could potentially influence their development.

Seven hundred and seven caucasians aged 1-82 years participated in a screening campaign at open-air recreation facilities in Austria. The volunteers underwent a total body examination by experienced dermatologists and answered a questionnaire. Clinical and dermoscopic images of one representative papillomatous naevus per person were taken.

Twenty-nine per cent of the volunteers exhibited papillomatous naevi, the highest frequency being found in young adults. No correlation between the frequency of papillomatous naevi and gender, skin type, sunburns, sunbed use or hormonal factors was found. Most lesions were brown papules (median diameter 5.0 mm), located on the trunk. Dermoscopy showed a predominance of homogeneous and globular pattern, multifocal hypo/hyperpigmentation and comma vessels. Of the papillomatous naevi, 9.8% showed suspicious scores with dermoscopic algorithms.

The lack of exogenous influencing factors and the predominance of globular dermoscopic pattern strengthen the hypothesis that papillomatous naevi belong to the same spectrum as small congenital melanocytic naevi. As the role of papillomatous naevi as precursors of melanoma remains unclear and they are frequently not recognized by the patients, one should perform dermoscopy of papillomatous naevi during skin cancer screening.