Nuclear β-catenin expression in basal cell adenomas of salivary gland

Abstract

Background: Nuclear localization of β-catenin is known in a wide variety of human neoplasms; however, there are few reports in basal cell adenoma of the salivary gland. Our objective was to confirm the nuclear localization of β-catenin in basal cell adenoma and to examine whether nuclear β-catenin expression could be a useful marker in the diagnosis of basal cell adenoma.

Methods: To evaluate the nuclear localization of β-catenin in basal cell adenomas, immunohistochemistry (IHC) and mutation analysis of CTNNB1 were performed in 22 and 21 cases, respectively. Mutation analysis of CTNNB1 in exon 3 was performed by DNA direct sequencing. In a comparative study, IHC for β-catenin was also performed in 157 other salivary gland tumors.

Results: Nuclear β-catenin expression was examined in 22 basal cell adenomas; scores were 2+ in 18 cases (81.8%), 1+ in three cases (13.6%), and 0 in one case (4.5%). Expression was localized in the basaloid myoepithelial cells. CTNNB1 mutation analysis was performed in 21 basal cell adenomas; mutations, including I35T and T41P, were detected in 11/21 (52%) cases. In comparison with other salivary gland tumors, one of three basal cell adenocarcinomas showed nuclear β-catenin expression, whereas there was no nuclear β-catenin expression in 154 other salivary gland tumors.

Conclusions: We demonstrated nuclear β-catenin expression and activation of the CTNNB1 gene in basal cell adenoma. Although nuclear β-catenin expression may be unable to distinguish basal cell adenoma from basal cell adenocarcinoma, it should be a helpful marker in the diagnosis of basal cell adenoma.