TPX2 is a microtubule-associated protein and is required for microtubule formation at kinetochores in mammalian cells. The purpose of this study was to clarify the expression of TPX2 mRNA and correlation between TPX2 and clinicopathological factors in salivary gland carcinomas. The expression of TPX2 mRNA was investigated in 20 human salivary gland carcinomas (8 mucoepidermoid carcinomas, 7 adenoid cystic carcinomas, 5 acinic cell carcinomas) and 6 normal submandibular glands using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). The mean expression level of TPX2 mRNA was higher in mucoepidermoid carcinomas (0.53+/-0.51) than in normal submandibular glands (0.047+/-0.029); a significant association was found (Mann-Whitney U test, P=0.0067). The mean expression levels of TPX2 were also higher in acinic cell carcinomas (0.45+/-0.49) and adenoid cystic carcinomas (0.28+/-0.22) than in normal submandibular glands. Statistical correlations were found (Mann-Whitney U test, P=0.028 and P=0.003, respectively). Correlation between expression of TPX2 and receptor for hyaluronan-mediated motility (RHAMM) was also investigated in this study. A significant association was found between the mRNA expression levels of TPX and RHAMM (Pearson's correlation coefficient by rank test, P=0.020). These results indicate that human TPX2 mRNA is closely linked to increased or abnormal cell proliferation in malignant salivary gland tumors.