Unusual solitary neurofibroma on the lower lip of a child.

Neurofibromas (NF) are benign tumors with involvement of the peripheral nerve, which is not frequently located in the oral cavity, and especially, extraordinary rarity on lower lip of a child. This report describes a case of a NF on lower lip in a 12-year-old Brazilian child. NF consists of a wide variety of cell types, including Schwann cells, perineurial cells, and fibroblasts. Due to cellular heterogeneity, several hypotheses have been proposed to explain the histogenesis of this lesion. One of them, it support an origin of Schwannian, while others emphasize the participation of both Schwann cells and perineural cells. Excisional biopsy was performed to establish definitive diagnosis. Microscopically, the lesion was composed of interlacing bundles of elongated cells with wavy nuclei and small nerve fibers. Immunohistopathologic assessment showed cells positive for S-100, confirming the diagnosis of NF. No recurrence was observed after 1-year follow-up. Pediatric dentists must have a thorough knowledge of this unusual lesion.