Assessment of CTNNB1 gene mutations and β-catenin immunoexpression in salivary gland pleomorphic adenomas and adenoid cystic carcinomas

Abstract

β-Catenin exerts multiple functions in several neoplasms, playing a major role in cell signaling and tumor progression. This study analyzed possible CTNNB1 mutations in salivary gland pleomorphic adenomas (PAs) and adenoid cystic carcinomas (ACCs), and determined possible differences in β-catenin immunoexpression in relation to these mutations, as well as histopathological aspects of these tumors. Twenty-four PAs (15 cell-rich and 9 cell-poor tumors) and 24 ACCs (10 tubular, 8 cribriform, and 6 solid tumors) were selected for the analysis of β-catenin distribution and cellular localization. Furthermore, β-catenin expression was evaluated using the H-score scoring system. Mutations in CTNNB1 exon 3 were investigated by the single-strand conformational polymorphism test. Diffuse β-catenin expression was more frequently observed in ACCs compared to PAs (P = 0.008). No significant difference in β-catenin cellular localization was observed between these tumors (P = 0.098). Comparisons between PA and ACC cases revealed a higher median H-score in the latter (P = 0.036). Cell-rich PAs exhibited a trend for higher H-score than cell-poor tumors (P = 0.060), whereas lower H-scores were observed in cribriform ACCs when compared to tubular and solid ACCs (P = 0.042). Mutations in CTNNB1 were observed in 6 PAs and 7 ACCs, with no significant difference in H-scores for β-catenin according to mutation status (P = 0.135). β-Catenin is important in the pathogenesis of salivary gland PAs and ACCs. In addition, CTNNB1 exon 3 mutations do not seem to significantly influence β-catenin cytoplasmic/membranous expression or nuclear translocation in these tumors.

Keywords: Adenoid cystic carcinoma; Immunohistochemistry; Mutation; Pleomorphic adenoma; Salivary gland neoplasm; β-Catenin.