Cutaneous intraneural glomus tumor.

The unusual occurrence of a glomus tumor within a small, deep dermal nerve is reported. This phenomenon has been described previously only once in the literature. The lesion appeared as a painful cutaneous nodule in the shoulder of a 67-year-old woman. Microscopically, a typical solid, smooth muscle actin-positive glomus tumor was seen, encircled completely by neural tissue in the deep dermis. There was no extension of the tumor beyond the nerve. Immunohistochemically, the nerve fibers surrounding and within the tumor were positive for S-100 protein and neurofilament. The presence of perineurium surrounding the glomus tumor was confirmed by a layer of epithelial membrane antigen-positive cells. In view of the absence of normal glomus bodies in the nerves, an origin from a less specialized perivascular cell is proposed.