Fibrous papule: an immunohistochemical study with an antibody to S-100 protein.

We studied twenty biopsies taken from fibrous papules which were located in the central part of the face. The lesions, which were characteristic histologically, did not contain S-100 protein within the stellate cells in the papillary dermis, nor was this substance found in mesenchymal cells with some features of nevus cells. In control studies, S-100 protein was found using an unlabeled antibody peroxidase-antiperoxidase technic within nevus cells composing junctional intradermal, and compound nevi, Spitz nevi, and halo nevi. It therefore seems unlikely that fibrous papule represents a form of degenerated nevus as some investigators have proposed.