Differential expression of S100 calcium-binding proteins in epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas

Aims: To investigate whether epidermoid cysts, branchial cysts, craniopharyngiomas and cholesteatomas express S100 proteins differentially by immunohistochemical assaying the presence of S100A1, S100A2, S100A3, S100A4, S100A5, S100A6 and S100B. Methods and results: Immunopositivity/negativity was recorded for each S100 protein in a series of 52 cases consisting of 12 epidermoid cysts, 12 branchial cysts, 15 adamantinomatous craniopharyngiomas and 13 acquired cholesteatomas. Except in the case of the craniopharyngiomas, immunoreactivity was assessed independently in the basal membrane and the basal, the internal and the keratin layers. Our data show that in contrast to S100B, which was rarely expressed, S100A1, S100A2, S100A4 and S100A5 were often present in these four types of epithelial lesions. S100A3 and S100A6 and, to a lesser extent, S100A5 were the most differentially expressed proteins across the different histopathological groups analysed. These three proteins are expressed more often in craniopharyngiomas and cholesteatomas, the two more aggressive types of lesions. Conclusions: This is the first study to report data on the expression of seven S100 proteins in different histopathological groups of epithelial head and neck lesions, whose precise embryological origins are still a matter of debate. S100 proteins could possibly be used as markers to target this embryonic origin, since our results show that S100A3 and S100A6 (and, to a lesser extent, S100A5) are expressed differentially across these different groups of epithelial lesions.