CLINICAL AND DERMOSCOPIC CHARACTERISTICS OF MELANOCYTIC NEVI IN PREPUBERTAL CHILDREN

Abstract

SUMMARY D ermoscopy is a non-invasive technique that allows physicians to observe structures and colors not otherwise visible to the unaided eye. The conventional dermoscopic diagnosis is based on the assessment of specific criteria and on the application of different diagnostic algorithms. In recent years, polarized light dermoscopes gradually overtook non-polarized light devices. Dermoscopy is not too time-consuming. The time for dermoscopic examination of nevi is basically double that required for a naked-eye examination, but still under 3 minutes that is a reasonable time for a correct skin cancer screening and reduces the number of unnecessary biopsy. Dermoscopy also allows us to study the physiology of nevi. Some people have a high propensity to develop nevi, others lower, and this propensity is genetically established and, in part, due to environmental factors. The number of nevi is small in childhood, increases during adolescence and mid-life, and finally decreases during late adulthood. The dermoscopic pattern of nevi seems to be age- and site related. Children, like their adult counterparts, often present to the dermatologist with pigmented lesions that are new or changing. Unique to the pediatric population, however, is that they are in a dynamic growing phase of life. One sign of this dynamic phase is manifested by the development, growth, and occasional involution of nevi. Although there are many different classification schemes depending on the method to obtain the morphologic information, the most widely used scheme divides melanocytic nevi according to their clinical history into congenital and acquired nevi. By definition, congenital melanocytic nevi are present at birth or soon thereafter, although some small congenital nevi are clearly tardive in their clinical presentation. Current opinion holds that some elements of such nevi are present at birth but remain inconspicuous until some later date. Based on the definition of a congenital nevus, the group of acquired nevi encompasses basically all other benign melanocytic proliferations with development after birth. In contrast to congenital nevi, not the size but the number and clinical variability of acquired nevi are the most important risk factors for the development of melanoma. Furthermore, considerable confusion arises in differentiating small congenital nevi from acquired nevi as many nevi with histopathologic criteria suggestive of small congenital nevi are actually not present at birth. Currently, there are different classification schemes that are dependent on the method of obtaining morphological information. While clinical (non dermoscopic) classification involves flat, elevated and nodular types, dermoscopy identifies globular, reticular or structureless morphologies, with various combinations of these features as subtypes. Briefly, the new concept states that nevi develop via two different pathways, namely an endogenous (origin from dermal melanocytes) and exogenous (origin from epidermal melanocytes) pathway. The former leads to nevi that develop in early childhood and persist throughout a person's lifetime, revealing a dermoscopic globular pattern, while nevi with an epidermal origin develop mostly at puberty due to exogenous factors, such as UV exposure, and show a dynamic life-cycle. These latter nevi exhibit a reticular pattern by dermoscopy.