Three mammalian hyaluronan synthase (HAS) genes, HAS1, HAS2, and HAS3, are involved in hyaluronan biosynthesis [9], and their expressions vary depending upon tissue-, age- and pathophysiological differences and are important to investigate the biological function of hyaluronan, especially in tumor cell malignancy, because the overexpression of HAS makes tumor cells more aggressive with significant differences in the malignant activity among the three HAS genes [10]. The gene discussed is HAS1; the disease is neoplasm.