Expression of Mcm-2, Ki-67 and geminin in benign and malignant salivary gland tumours

BACKGROUND: Recent studies have proposed that minichromosome maintenance (Mcm) proteins may be sensitive proliferation markers and may serve as novel biomarkers for prognostication and diagnosis of various pre-malignant and malignant lesions. The aims of this study were to determine the expression of Mcm-2, Ki-67 and geminin in salivary gland (SG) tumours, and to evaluate their usefulness for diagnosis or for prediction of tumour behaviour. METHODS: Tissue from 62 SG tumours was assembled in tissue microarray format. There were 13 adenoid cystic carcinomas (ACC), 10 carcinoma ex pleomorphic adenomas (CEPA), 10 mucoepidermoid carcinomas (MEC), 10 polymorphous low-grade adenocarcinomas (PLGA), 10 pleomorphic adenomas (PA) and nine acinic cell carcinomas (AcCC). Clinicopathological data were collected retrospectively and immunohistochemical analyses of Mcm-2, Ki-67 and geminin were performed on all lesions. Labelling index (LI) for each marker was determined by counting the percentage of positive cells in six random fields from three arrays per case. RESULTS: Mcm-2 expression was higher than Ki-67 and geminin in all tumours studied. Mcm-2 LI was higher in ACC (28.2 +/- 19.2%) than in CEPA, AcCC, MEC, PA and PLGA (5.3 +/- 4.1%, P = 0.001). Mcm-2 LI was higher in CEPA (20.4 +/- 5.0%) than in PA (6.9 +/- 5.0%, P = 0.001). LI did not correlate to tumour grade or outcome for any of the markers or tumour types. CONCLUSIONS: The findings suggest that Mcm-2 may be a sensitive proliferation marker in SG tumours and may be useful for differential diagnosis between PA and CEPA, and ACC and PLGA. Further studies are warranted to assess the value of Mcm-2 as a predictor of recurrence and survival.