Hyaline cells in chondroid syringomas. A light-microscopic, immunohistochemical, and ultrastructural study

The origin and significance of hyaline cells (HC) in chondroid syringomas (CS) is unclear. In a review of 20 CS, we found HC in eight cases. These were studied immunohistochemically, using antibodies to cytokeratin, vimentin, carcinoembryonic antigen, epithelial membrane antigen, desmin, muscle-specific actin, S-100 protein, myoglobin, alpha-1-antitrypsin, chromogranin, glial fibrillary acidic protein, and neuron-specific enolase. HC gave a positive reaction to cytokeratin, vimentin, S-100 protein, and neuron-specific enolase, but not to the other antibodies. Thioflavin-T stain for amyloid was negative. Ultrastructurally, HC contained intermediate filaments in hap-hazard arrangement without specific structures or densities, and had sparse intracytoplasmic organelles and rare desmosomal attachments. Intermediate forms between epithelial cells and HCs were also identified. Our results suggest that HCs are relatively common in Cs (40%) and are more frequent in CS with solid nests and myxoid stroma (relative frequency 62.5%). Immunohistochemically, HCs of CS have a specific phenotype profile; however, ultrastructurally, HCs of CS are not distinct and are similar to HCs in other organs. These results do not suggest an exclusive myoepithelial origin of HCs; it appears that HCs could derive from any epithelial cell type of sweat glands, probably via a regressive process.