More than 90% of the oral cancer is histopathologically squamous cell carcinoma (SCC). According to the clinical behavior and histopathological features, we hypothesize that oral SCC (OSCC) is originating from either oral squamous epithelium or minor salivary glands. In this study, we attempted to clarify the possibility, in which some of the OSCC was originating from minor salivary glands, and whether these tumors showed aggressive biological behavior. The mRNA expression profile of the samples obtained from six patients with OSCC (5 men, 1 woman, mean age: 62.7) was analyzed by the microarray containing 29,098 genes. Clustering analysis by the expression level of the 917 genes, which were differentially expressed in normal oral squamous epithelium and normal salivary glands, revealed that 6 samples can be divided into 2 groups. The expression profile of 4 cases was similar to that of normal oral squamous epithelium, and that of 2 cases was similar to that of normal salivary glands. Furthermore, we identified 11 genes from the 917 genes which can easily determine the origin of the OSCC. Subsequently, we examined the expression levels of 11 marker genes in 73 OSCCs by RT-PCR and determined the origin of the OSCC. In 73 OSCCs, 13 tumors (18%) were considered to be originating from minor salivary glands, and these tumors showed highly metastatic potentials (61.5% vs. 31.7%) and poor over-all survival rate (38.5% vs. 21.7%). In conclusion, determination of the origin of the OSCC is helpful to make a treatment plan for the patients with OSCC.

Conflict of interest: None declared.