Cutaneous solitary neural hamartoma: report of an unusual case.

Cutaneous hamartomas are tumor-like proliferations of tissue indigenous to the organ but arranged abnormally. There are examples in the literature of cutaneous hamartomas composed of a variety of different components. To our knowledge, there is no previous report of such cutaneous solitary neural hamartoma. Our case occurred in a 51-year-old man with pain and paresthesia in the right shoulder associated with a nodule that was surgically removed. There was no history of trauma, other skin nodules, neurofibromatosis, or tuberous sclerosis. Histologically, there was an unencapsulated nodule, composed of mature nerve bundles noted abnormally high within the papillary dermis, extending to the reticular dermis with periadnexal distribution. Immunohistochemically, the nerve bundles were positive for S-100, including the smaller nerve twigs, and the perineurium was highlighted by epithelial membrane antigen, reminiscent of normal peripheral nerves. Although, neural components including mature nerve bundles have been described in various cutaneous hamartomas, this represents a peculiar case of a cutaneous mature peripheral nerve hamartoma. Whether this is related to other entities of cutaneous hamartomas (ie, neurofollicular hamartoma, folliculosebaceous cystic hamartoma) is not yet apparent, although it is probably a unique entity.