The purpose of this study is to investigate the correlation between DNA methylation and the treatment and recurrence of oral cancer.

In this study, investigators plan to recruit 40~50 patients who had, or currently has oral cancer. The study procedures are as below:

• After the Informed Consent Form is signed, swab from the lesion site and normal site to obtain oral epithelial cells.
• Collect tissue from the tumor site and the non-cancerous matched site from the surgery or the tissue bank.
• Collect oral swab from the lesion site and the normal site when patients return to the clinic for a regular follow-up.

Specimens will be collected for DNA methylation testing, and the results will be compared with patient's clinical diagnosis. It is expected that the relationship between DNA methylation, oral cancer, and the recurrence of oral cancer will be found.

Inclusion Criteria:

• Age between 20 and 75 years old
• Had or currently has cancer of the oral cavity
• Agree to sign the Informed Consent Form (ICF) and comply with follow-up procedures

Exclusion Criteria:

• Unwilling to sign the Informed Consent Form (ICF)
• Has an autoimmune disease of the oral cavity

Investigators plan to retrieve the tissue from the biobank in Taipei Veterans General Hospital or recruit oral cancer patients in this study over six months. The total patient number are 40-50. Specimen types include non-cancerous matched tissues, cancer tissues, and the oral swab. DNA methylation for several genes will be tested by using standardized reagents and instruments.