Immunohistochemical analysis of keratin expression in clear cell syringoma. A comparative study with conventional syringoma.

Immunophenotypes, especially expression of cytokeratins, in 9 cases of clear cell syringoma were examined using antibodies against epithelial membrane antigen (EMA), and 17 kinds of monoclonal anti-keratin antibodies to investigate its histogenesis. In addition, 7 cases of conventional syringoma were selected for parallel assessment. Conventional syringoma expressed CK1 and CK10, which exists in the acrosyringium and the transitional portion between the acrosyringium and the dermal duct. Based on immunostaining with RCK102 and 35 beta H11, syringoma was thought to express CK5. Because expression of CK5 was observed in the basal cells of sweat duct ridge (lower acrosyringium) and the outer cells of the dermal duct, but not in the acrosyringium located at upper epidermis, we speculated that syringoma differentiated toward the transitional portion between the acrosyringium and the dermal duct. A comparative study of keratin expression between conventional and clear cell syringoma showed that there was no difference in the immunoreactivities. Based on the above observations, we confirmed that clear cell syringoma is a metabolic variant of conventional syringoma, and differentiates into the transitional portion between the acrosyringium and the dermal duct.