Clear cell papulosis: an immunohistochemical study to determine histogenesis.

Clear cell papulosis is a rarely described disease characterized by multiple white maculopapules. Histopathologically, diagnostic clear cells are seen mainly among the basal cells of the epidermis. The origin of the clear cells has been thought to be eccrine or apocrine secretory cells in the epidermis because of the positive immunostaining with anticytokeratin antibody AE1, carcinoembryonic antigen (CEA), epithelial membrane antigen, and gross cystic disease fluid protein-15. IKH-4 and CEA have been reported to stain the eccrine secretory cells, but not the apocrine secretory cells. On the contrary, lysozyme has been reported to stain apocrine glands, but not eccrine glands. CAM5.2 has been reported to show a positive reaction to staining in secretory cells of eccrine glands, but only occasional weak staining in the inner surface of eccrine ducts. In our study, the clear cells in the epidermis stained with IKH-4, CEA and CAM5.2, but not with lysozyme. These results suggest that the clear cells may be eccrine secretory cells.