Ultrastructure of chondroid syringoma: role of the myoepithelial cell in the development of the mixed tumor of the skin and soft tissues.

The ultrastructure of a chondroid syringoma is described. The tumor nests are formed by clumps, solid cords and tubular structures distributed diffusely throughout a stroma of varying density. Two different types of cells form this tumor: dark cells forming the inner layer of the tubuloalveolar and ductal structures and having epithelial features, and light cells which form the outer layer of the tubular structures and show myoepithelial differentiation. The myoepithelial cells seem to be responsible for the production of the chondroid areas and thus the mixed appearance of the tumor. The epithelial cells forming the solid nests of the tumor show intracytoplasmic luminal formation and other features that favor the origin of chondroid syringoma from the eccrine sweat gland duct.