Spindle or epithelioid melanocytic (Spitz) nevi usually affect children or adolescents and growth in the face or the lower extremities. Histologically, they may show cytoarchitectural atypia and mitotic figures that could represent diagnostic pitfalls with malignant melanoma. Atypical spitzoid tumors (AST) indicate lesions that microscopically show intermediate characteristics between benign nevi and malignant melanoma. Nestin expression has been evaluated in benign nevi and malignant melanoma, but no studies on its role in Spitz lesion have been elaborated so far. Our results indicate that Nestin could allow to discriminate between AST and malignant spiztoid melanoma; the typical dermoscopic pattern is also associated with benign nevi in contrast to the atypical pattern that accumunates AST and malignant spitzoid melanoma.

Patients with multiple atypical nevi are at higher risk of developing melanoma. Among different techniques, sequential digital dermatoscopic imaging (SDDI) is a state-of-the art method to enhance diagnostic accuracy in evaluating pigmented skin lesions. It relies on analyzing digital dermatoscopic images of a lesion over time to find specific dynamic criteria inferring biologic behavior. SDDI can reduce the number of necessary excisions and finds melanomas in an early-and potentially curable-stage, but precautions in selecting patients and lesions have to be met to reach those goals.

Significant progress in the molecular pathology of melanocytic tumors have revealed that benign neoplasms, so-called nevi, are initiated by gain-of-function mutations in one of several primary oncogenes, such as BRAF in acquired melanocytic nevi, NRAS in congenital nevi or GNAQ/GNA11 in blue nevi, with consequent MAPK and PI3K/AKT/mTOR activation. Secondary genetic alterations overcome tumor suppressive mechanisms and allow the progression to intermediate lesions characterized by TERT-p mutation or to invasive melanomas displaying disruption of tumor suppressor genes. Currently, melanoma is molecularly regarded as four different diseases, namely BRAF, NRAS, NF1 and the "triple wild type" subtypes, which are associated with particular clinicopathological features. Melanocytic Spitzoid lesions include benign Spitz nevus, atypical Spitz tumor (AST) and Spitzoid melanoma. This is a challenging diagnostic group, particularly with regard to the distinction between AST and Spitzoid melanoma on clinical and histological grounds. Molecular analysis has identified the presence of HRAS mutation, BAP1 loss (often accompanying by BRAF mutations) or several kinase fusions in distinct categories of Spitz tumors. These aberrations account for the rapid growth characteristic of Spitz nevi. Subsequent growth is halted by various tumor suppressive mechanisms abrogation of which allow the development of AST, now better classified as low-grade melanocytic tumor. Although at present ancillary genetic techniques have not been very helpful in the prediction of biological behavior of AST, they have defined distinct tumor subsets differing with regard to biology and histology. Finally, we discuss how novel molecular markers may assist the differential diagnosis of melanoma, particularly from malignant peripheral nerve sheath tumor (MPNST). It is anticipated that the significant progress in the field of molecular pathology regarding the various types of melanocytic tumors, will eventually contribute to a more accurate histologic categorization, prediction of biologic behavior and personalized treatment.

We report the case of a newborn boy with multinodular NRAS and BRAF mutation-negative congenital melanocytic nevi and cerebral lesions compatible with congenital intraparenchymal melanosis. Histopathology from skin lesions showed atypical nodular melanocytic proliferation with marked melanocytic atypia and a large number of mitoses and apoptosis, indicating aggressive proliferation. The child developed several new subcutaneous tumors and multiple internal lesions, which were confirmed to be metastases, and died at 5 months of age. This case may represent an infantile melanoma developing from a giant congenital melanocytic nevus or a congenital melanoma.

Dear Editor, There are few literature data about nevi in patients with a history of toxic epidermal necrolysis (TEN) and little recommendations for follow-up and risks of melanoma (MM). Eruptive melanocytic nevi (EMN) is a rare phenomenon that has been associated with bullous disorders, immunosuppression, and immunodeficiency, but in some cases can occur without precipitating factors (1). The etiology is largely unknown, but there is evidence that immunosuppression might play a crucial role in nevogenesis, probably due to the inability of the immune system to inhibit melanocytic (MC) proliferation (2,3). We report the follow-up of a patient with a history of TEN who later developed atypical nevi. A 17-year-old man with a history of severe TEN two years earlier, most probably due to valproic acid and diclofenac, was referred to our Department due to atypical nevi. The patient presented with scars, scattered pigmentation (Fig. 1), and symblepharon as a consequence of TEN (Fig. 2). Most of his nevi developed in following two years after TEN. During the first visit in 2009, clinical and dermoscopic photodocumentation was performed. The patient presented with a moderate number of nevi (Fig. 3), dermoscopically subclassified as globular. One atypical MN was found on the back, with dermoscopic findings of reticular pattern and presence of suspected areas of regression (Fig. 4. a, b), and it was excised to rule out melanoma (Fig. 4, Fig. 5). The patient did not come to regular follow-up from 2009 to 2014, and presented in 2014 which was when comparative photo documentation was made. As this visit another, speckled type of newly-occurred nevus was excised. Both excised nevi were histopathologically characterized as dysplastic. Only a few references are available on nevi development after TEN. Anticonvulsives and NSAIDs, as in our case, are often involved in the etiopathogenesis of TEN (4,5). Survivors may experience a variety of long-term complications; authors reported that 19% of their patients developed new nevi after TEN (6,7). EMN develop several years after TEN as a suddenly arising large number of nevi that may resemble speckled lentiginous nevi (8). Histologically. EMN demonstrate a proliferation of MC at the dermo-epidermal junction and, if compound, in the papillary dermis, arranged mostly in nests. Junctional MC may appear slightly pleomorphic, but no significant cytological atypia or prominent pagetoid spread of MC was reported (9). EMN have been associated with a specific dermoscopic finding of a symmetrical peripheral rim of globules which represent pigmented junctional nests of MC in the periphery and are a specific feature of rapidly enlarging MC nevi (10,11). The pathogenesis of EMN is not known. The microenvironment of epidermal regeneration may have some effects on MC because MC hyperplasia develops after cutaneous trauma (observed in recurrent nevi). The cytokines and growth factors produced and secreted during epidermal regeneration might contribute to the proliferation of residual epidermal MC and subsequent nevus formation (12). Because most of the bullous disorders associated with EMN are transient, the authors believe that changes in local growth factors may also be temporary and MN remain stable without a propensity to malignant degeneration without further stimuli (13). This is corroborated by the fact that no reports of malignant change of EMN in patients with bullous disorders have been described. It is likely that the etiology and natural course of EMN differs between two main populations of patients, with EMN arising after bullous disorders being more likely to remain benign compared with those with ongoing immunosuppression, but this hypothesis has yet to be proven. The actual risk of MM in patients with EMN remains unknown. Since our patient did not have many nevi, he does not fit into the EMN category. Due to the atypical appearance of his nevi, long-term follow-up on 6-month basis is recommended.

BRCA1-associated protein 1(BAP1) inactivated melanocytic nevi are pink to tan and dome-shaped in clinical appearance, resembling dermal nevi, but with distinct histologic features of two melanocytic subpopulations: larger atypical melanocytes and nests of smaller, blander nevoid melanocytes. Pedigrees with BAP1 mutations are at greater risk of various malignancies. We report the case of a 16-year-old boy with multiple benign-appearing nevi, all demonstrating loss of BAP1 on immunohistochemistry. History revealed that his father had died of paraganglioma, which is also associated with BAP1 mutations.