Objectives: The aim of this study was to determine the expression of PLUNC proteins in benign and malignant salivary gland tumours and thus their potential use as diagnostic and / or prognostic tools.
Materials and methods: A tissue microarray was assembled from 64 salivary gland tumours including adenoid cystic carcinoma, carcinoma ex-pleomorphic adenoma, mucoepidermoid carcinoma, polymorphous low-grade adenocarcinoma, pleomorphic adenoma, acinic cell carcinoma, myoepithelial carcinoma and papillary cystadenocarcinoma. Clinicopathological data were collected retrospectively and immunohistochemical analysis of three PLUNC proteins (SPLUNC1, SPLUNC2 and LPLUNC1) was performed. Immunoreactivity was assessed as positive or negative.
Results: PLUNC expression was only found in mucoepidermoid carcinomas and papillary cystadenocarcinoma; all other tumours studied were negative. Mucin plugs, mucous and intermediate cells of mucoepidermoid carcinomas were positive for LPLUNC1 and SPLUNC2, but areas composed of epidermoid and clear cells were negative for all PLUNCs. Papillary cystadenocarcinoma was positive for all PLUNCs. No correlation was found with tumour grade or outcome.
Conclusions: Intense expression of two PLUNC proteins in mucous cells and mucin plugs of mucoepidermoid carcinoma and papillary cystadenocarcinoma indicate that they could be used as additional diagnostic tools in some equivocal cases, but further studies are needed to understand the biological processes involved in PLUNC expression.