Our data show, for the first time, the biphasic pattern of hyaluronan metabolism in lungtumors, and reveals increased hyaluronan synthesis in premalignant lesions followed byreduced hyaluronan content in squamous cell carcinoma and adenocarcinoma as aconsequence of decreased HAS expression and increased degradative Hyal-1 and −3. This evidence concerns the gene HYAL1 and squamous cell carcinoma.