Proliferating Neurocristic Hamartoma Arising in a Giant Congenital Nevus: Comparative Genomic Hybridization Findings.

Neurocristic cutaneous hamartomas (NCHs) are rarely reported tumors with divergent differentiation derived from persistently active pluripotent cells from the neural crest. They result from aberrant development of the neuromesenchyme, and they can express fibrogenic, melanocytic, and/or neurosustentacular differentiation. Thus, congenital melanocytic nevus also represents a neurocristic dysplasia of the skin in which cells are melanogenic cells arrested in development located in the reticular dermis, and nodular proliferative neurocristic hamartoma may arise within a congenital melanocytic nevus. The real importance of NCHs is that, although few cases have been reported in the literature, some cases have shown development of melanoma. Moreover, the only previously reported case of a similar "proliferative neurocristic nodule" analyzed with comparative genomic hybridization showed an aberration pattern similar to melanoma. We present a rare case of NCH associated with a congenital nevus in a 7-year-old boy, with classical histological and immunohistochemical features suggesting a "proliferative neurocristic hamartoma". Comparative genomic hybridization assay showed that chromosomal aberrations were absent in the congenital nevus, whereas, interestingly, the proliferative neurocristic proliferation had an aberration pattern similar to proliferative nodules with gains or losses of entire chromosomes only, similar to typical proliferative nodules and supporting the benign behavior of this lesion.