MAML2 rearrangement in Warthin’s tumour: a fluorescent in situ hybridisation study of metaplastic variants

Abstract

Warthin's tumour (WT) is a common benign lesion of the major salivary glands. The nature of WT remains controversial, with particular regard to the presence of clonal chromosomal abnormalities, including the t(11;19) translocation involving the CRTC1 and MAML2 genes, that have been identified in both WT and mucoepidermoid carcinoma. In this study, we focused our attention on metaplastic WT variants, and we conducted a fluorescent in situ hybridisation (FISH) analysis for the presence of MAML2 gene rearrangement. Dual-colour FISH analysis was performed on paraffin-embedded sections of eight WTs showing metaplastic changes (five with squamous metaplasia, two with mucinous metaplasia and one with both) using a MAML2 break-apart probe. Presence of split signals indicative of gene rearrangement was identified in a subset of cells in areas of squamous metaplasia in two samples of WT. No rearrangement was observed in the oncocytic epithelium, in lymphocytes and in areas of mucinous metaplasia. The presence of a small subpopulation of cells carrying MAML2 rearrangement in areas of squamous metaplasia within WT could predispose these lesions to malignant transformation in mucoepidermoid carcinoma and could represent a molecular link between the two entities.