Surface microscopy features of congenital nevi

Congenital melanocytic nevi (CMN) are pigmented skin lesions (PSL) that are present at birth. The frequency of PSLs at birth is estimated to be 2.5%, and 1% of newborns have biopsy-confirmed melanocytic nevi.[1, 2 and 3] The most widely used classification of congenital nevi is based on their size, subdividing the lesions into three groups: small (<1.5 cm), medium (1.5–19.9 cm), and large (20 cm or greater). [4] It is well established that giant congenital nevi have a potential risk of malignant transformation, and the probable lifetime risk is quoted between 5% and 15%. [4, 5, 6, 7, 8 and 9] Small and medium-size CMNs (SCMNs) are considerably more common than large ones and are thus of greater epidemiologic significance if they represent precursors of melanoma. The risk for the occurrence of melanomas in SCMNs, however, is still under debate. [3, 4, 10, 11, 12, 13, 14 and 15] The problem is that until the SCMN cannot be precisely diagnosed because of the lack of specific clinical and histologic criteria and the frequent unreliability of patient history, their melanoma risk cannot be evaluated. In fact, ascertainment of congenital nevi beyond the newborn period may be difficult because the prevalence of acquired nevi rises rapidly during early childhood. Although histologic examination is useful in distinguishing whether or not a nevus is congenital or acquired, there are no features that are completely specific and sensitive. [16] A careful history, therefore, is at times more sensitive than histologic examination in diagnosing a nevus as congenital, although the reliability of anamnesis regarding the congenital nature of the lesion cannot always be proven.Yet, this issue is of practical importance: routine prophylactic removal of all SCMNs has been suggested by some authors,[6, 8 and 12] and it is necessary to balance the cost and risk of surgery with any possible risk of malignant change. The introduction of instrumental devices allowing the observation of subsurface structures has enabled the identification of morphologic features characterizing different pigmented skin lesions. [17, 18, 19, 20, 21 and 22] Therefore, the identification of specific surface microscopic aspects of SCMNs appears to be relevant to correlate different morphologic subgroups to different risk classes in prospective studies assessing the incidence of melanomas arising from CMNs.We recently proposed a classification of SCMNs according to their macroscopic and surface microscopic appearance.[23] The following data refer to a series of SCMNs (mean diameter of 18 mm) that were examined and recorded by means of a polarized-light surface microscope using 20-fold images for the description of the global aspect of the lesion and 50-fold ones for identification of the characteristic patterns. An equal number of acquired melanocytic nevi randomly selected from our database was examined for comparison of the two series of PSLs. Images were acquired by a VMS-110A videomicroscope (Scalar, Mitsubishi, Japan), based on the polarizing-light method [24] and the Videocap 8.09 (DS-Medica, Italy) software.