SO-CALLED NEOPLASTIC MYOEPITHELIAL CELLS IN CHONDROID SYRINGOMAS MIXED TUMORS OF THE SKIN - THEIR SUBTYPES AND IMMUNOHISTOCHEMICAL ANALYSIS

An immunohistochemical study of nine cases of chondroid syringomas/mix ed tumors of the skin was performed to elucidate the nature of the so- called neoplastic myoepithelial cells (NMEC) in tumor tissues. These n ine tumors contained NMEC of considerable variability in number from o ne tumor to another. These NMEC were classified into three types: (i) hyaline cells (plasmacytoid cells); (ii) spindle NMEC; and (iii) polyh edral cells. They showed different immunostaining patterns, as the fol lowing describes. Cytokeratin 14 was positive in most of the spindle N MEC and a large number of the polyhedral cells, and in a small number of the hyaline cells. Concerning low molecular weight cytokeratins, mo st of the hyaline cells showed immunoreactivity, whereas they were neg ative in many of the spindle NMEC and were expressed only in a small n umber of the polyhedral cells. alpha-Smooth muscle actin and muscle-sp ecific actin were positive in the spindle NMEC but negative in any of the hyaline cells and polyhedral cells. These findings strongly indica te that the hyaline cells and the spindle NMEC are of the simple epith elial and myoepithelial types, respectively. The findings also suggest that the polyhedral cells show differentiation toward basal cells of the sweat gland dermal ducts or myoepithelial cells.