Clear cell papulosis of the skin. A new entity with histogenetic implications for cutaneous Paget's disease.

A new skin condition characterized by multiple white papular eruptions was observed in two young brothers. Histologic study revealed many benign pagetoid clear cells in the basal layer of the acanthotic epidermis with decreased pigmentation. These cells contained cytoplasmic mucin and were positive for keratin AE1/AE3, carcinoembryonic antigen, and epithelial membrane antigen. The staining pattern was identical to that of extramammary Paget's disease. The presence of mucin granules and cytoplasmic filaments corresponding to AE1/AE3 were confirmed ultrastructurally. Comparative histochemical and immunohistochemical studies with normal eccrine sweat glands, Toker's nipple clear cells, and Paget cells of mammary and extramammary Paget's disease suggest that these clear cells are an aberrant derivative of sweat-gland epithelial cells in the epidermis. AE1/AE3 is an excellent marker for the "clear cells" of both the condition described and the cells in the nipple. The term "clear cell papulosis" is proposed for this new entity. The clear cell identified provides evidence for the existence of potential precursor cells in the epidermis for cutaneous Paget's disease.