[Chondroid syringoma. Immunohistologic indications of myoepithelial differentiation]

Chondroid syringoma belongs to the group of so-called mixed tumors, like pleomorphic adenomas of the lacrimal and salivary glands. The histogenesis of this tumour is still disputed, in particular with respect to its stromal component. The distribution of cytokeratins (CKs), CEA, EMA, vimentin, S-100 protein, desmin and actin [alpha-smooth muscle actin (alpha-SMA)] was investigated by immunohistological examination of paraffin sections from a chondroid syringoma of the apocrine type. The neoplastic formations have been classified into tubuloalveolar structures, solid nests/aggregations and stromal cells of varying morphology. The inner-most cells of tubuloalveolar structures were characterized by marked expression of CKs (KL1 and MNF116), CEA and EMA, while in the outer ones there was moderate expression of vimentin, S-100 was expressed to a lesser extent and KL1, weakly but there was marked and consistent expression of MNF116. Whereas the solid nests expressed vimentin, S-100 protein, MNF116 markedly and KL1 weakly, the stromal cells were consistently positive for vimentin, S-100 protein and, focally, CKs and alpha-SMA. Anti-alpha-SMA specifically detects myoepithelial cells. In addition, the partly overlapping immunoreactivity of the intermediate filaments, membrane proteins and proteins in the different structures may indicate a common clonal origin of all neoplastic cells in chondroid syringoma.