Suggested causes of nasopharyngeal cancer are the consumption of salted fish, EBV infection, and genetic factors. Cytogenetic studies have shown that there are multiple aberrations in chromosomes 1, 3, 11, 12, and 17 in nasopharyngeal cancer. Loss of genetic material has been seen at defined loci in 3p, 9p, 11q, 13q, and 14q.15 In contrast with other head and neck cancers, mutations of the p53 and retinoblastoma (Rb) genes were uncommon, and overexpression of the c-myc and Int-2 genes was frequent.16 The findings of molecular biology studies have some clinical applications. First, the targeted immune response is applicable in nasopharyngeal cancer. Tumor cells express EBV proteins EBNA1, LMP1, and LMP2. Adoptive immunotherapy has been used, employing EBV-specific cytotoxic T cells to kill the EBV, and, because of the association of EBV with nasopharyngeal cancer cells, this therapy also kills cancer cells.17 On the diagnostic side, molecular biology studies contribute to the identification of tumor markers. Polymerase chain reaction testing can now detect the DNA of EBV in the serum of patients with nasopharyngeal cancer, and the levels of DNA detected have been shown to correlate with stage, recurrence, and metastasis of nasopharyngeal cancer.18 Because of the cost of polymerase chain reaction testing, its application in clinical situations is still being studied.