Quantitative immunohistochemical fingerprinting of adhesion/growth-regulatory galectins in salivary gland tumours: divergent profiles with diagnostic potential

Aims: This study tests the hypothesis that histopathological fingerprinting of galectins, which are emerging multifunctional effectors in cell sociology, could refine the differential diagnosis of salivary tumours. Methods and results: We applied non-crossreactive polyclonal antibodies against galectin-1 (Gal-1), galectin-3 (Gal-3), galectin-7 (Gal-7) and galectin-8 (Gal-8) for immunohistochemical analysis of salivary gland tumours (72 cases with benign disease and 39 cases with malignancy) and 29 control specimens. The principal positivity of cases, the site of signal presence and the quantitative parameters concerning percentage of positive cells and labelling intensity were determined. Acinic cell and adenoid cystic carcinomas (specifically tubular and cribriform types) shared the expression signature of Gal-1, Gal-3 and Gal-8 presence combined with Gal-7 absence. Mucoepidermoid carcinomas presented a unique profile based on cytoplasmic Gal-1, Gal-3, Gal-7 and Gal-8 localization in the intermediate cells. Adenomas were separable from malignancy by a consistent decrease in the labelling index (LI) for Gal-7 and Gal-8 (LI Gal-7, P < 10-6; LI Gal-8, P = 0.001). When present, staining for the tumour suppressor p16INK4a coincided with Gal-1 presence. Conclusions: Expression profiling of the four tested galectins in salivary gland tumours revealed non-uniform staining patterns with discriminatory potential based on intracellular localization and quantitative aspects.