Metallothionein immunostaining in adenoid cystic carcinomas of the salivary glands

Metallothionein (MT) is a protein that has been studied in several tumors as a prognostic factor and as a potential myoepithelial cell marker in breast cancer. The aims of this study were to assess the immunohistochemical staining of MT in adenoid cystic carcinomas of the salivary glands (ACC), and to analyze possible morphological and quantitative variations among the solid, cribriform, and tubular histological subtypes. MT was investigated in 15 cases of ACC using the immunohistochemical technique. All of the cases expressed the MT antigen. This expression was noteworthy in cells depicting myoepithelial differentiation. ACC with predominant tubular pattern presented a significantly lower mean index of MT immunopositivity than did solid or cribriform subtypes, while these two latter groups did not differ in terms of MT expression. Our results suggest that MT may be an important tool for immunolocalization of myoepithelial tumor cells in salivary gland neoplasms.