Cutaneous Neurocristic Hamartoma Presenting as Cutis Verticis Gyrata

Cutaneous neurocristic hamartoma is a rare developmental complex melanocytic lesion of neural crest origin in the dermis and subcutis with diverse histological differentiation including melanocytic, neurosustentacular, and mesenchymal elements. Cutis verticis gyrata is a cerebriform thickening of the scalp manifesting as folds, ridges, or creases. We report a case of cutaneous neurocristic hamartoma of the scalp in a 20-year-old woman presenting as cutis verticis gyrata. Microscopically, the lesion involved the dermis and the subcutis. Dendritic pigmented melanocytes were seen in between the collagen bands. Plexiform islands consisting of cords and palisades of spindled cells were also apparent. Immunohistochemically, HMB-45 positivity was observed in the dendritic melanocytic cells. S-100 protein was positive in dendritic melanocytes and in the Schwannian cells. The stromal cells showed CD34 staining. This lesion is presented because of its rarity, unusual clinical appearance, and resemblance to both a neurocristic hamartoma and large plaque type of blue nevus.