Adnexal-centered giant congenital melanocyte nevus with extensive ganglioneuromatous component and trisomy 7

Adequate interpretation of clinical and histopathologic features of giant c ongenital melanocytic nevus (GCMN) in newborns is a continued challenge. A GCMN with three large nodules and three polypoid exophytic tumors presented in the dorsum of a female full-term newborn, the borders exhibiting a spot ted grouped pattern. Microscopic examination revealed a peculiar adnexal-ce ntered (eccrine sweat gland ducts, acrosiringia, and hair infundibula) comp ound nevus expressing pagetoid intraepidermal spreading of epithelioid mela nocytes. The nodules represented an extensive ganglioneuromatous component. The neurons and their neuropil were positive for neuron-specific enolase, S-100, synaptophysin, tyrosine hydroxilase, and PGP 9.5. In addition to the se components, a poorly differentiated, fusiform, low-mitotic rate populati on of cells undergoing epithelioid differentiation (and probably neuronal d ifferentiation) with nodular arrangement was also present in the polypoid t umors and deeper parts of the nevus, in part intermixed with the neurons. T hese cells were vimentin positive but S-100 negative. FISH studies revealed these cells to express three signals for the centromeric probe for chromos ome 7 whereas the neuronal component showed just two. Adnexal-centered arra ngement of melanocytes has not been emphasized in GCMN. Ganglioneuromatous differentiation has been rarely reported in this condition. Trisomy 7 in GC MN has been reported only once previously.