S-100 protein content of dermal and oral mucosal blue nevi.

Three common blue nevi from skin of the trunk and upper extremities, and 5 from oral mucosae were studied using an immunoperoxidase stain for S-100 protein. The skin lesions were uniformly negative whereas all of the oral mucosal lesions contained numerous positively stained dendritic cells. This difference may, in part, be explained by the different embryologic origins of the connective tissue stromas; the connective tissues of the head and neck are thought to be of neural crest origin whereas the connective tissues in the rest of the body are of mesodermal origin. These findings strengthen and refine the association between S-100 protein content and neural crest derivation.