Heterogeneity and multiple expression of intermediate filament proteins, S-100 protein and neuron specific enolase in skin mixed tumor.

Intermediate filament proteins, keratin (KL1, PKK1, K8.12) and vimentin, S-100 protein alpha and beta subunits and neuron specific enolase were evaluated immunohistochemically to determine their distribution patterns in the tumor components of mixed tumor of skin. Keratin proteins were distributed widely in tumor epithelial cells or modified myoepithelial (MME) or neoplastic myoepithelial (NME) cells. Luminal cells of the tubulo-ductal structure of the tumor mass showed positive staining of KL1 and PKK1 keratins and an infrequently positive reaction of MoAb K8.12. The outer or basal tumor cells were characterized by coexpression of K8.12 keratin, vimentin, S-100 protein and infrequently neuron specific enolase reactivity. Heterogeneity of keratin distribution was seen in tumor epithelial cells. MME cells or NME cells of skin mixed tumor showed coexpression of keratin and vimentin, and multiple expression of intermediate filament proteins, S-100 protein and neuron specific enolase. Hyaline and chondroid changed cells stained intensely to vimentin and S-100 proteins, as well as to neuron specific enolase. The authors evaluate the histogenesis of skin mixed tumor in relation to epithelial and myoepithelial cells of the sweat gland and their immunohistochemical findings.