jnci.oxfordjournals.org JNCI | Editorials 541

developed multiple preneoplastic lesions and synchronous (ie, those detected simultaneously) or metachronous (ie, those detected within a relatively short period) tumors in the squamous epithelium of the oral cavity, a phenomenon they termed “field cancerization.” They attributed these findings to tobacco carcinogens damaging the entire field at risk — the oral mucosa. Several years later, Strong et al. ( 2) extended this concept (and the clinical implications) to the entire upper aerodigestive tract. Multifocal primary tumors having similar histological appearance have been described in many organs but are especially common in lung cancer. In this issue of the Journal, Wang et al. ( 3) investigate the mechanisms by which these tumors arise. The results of these studies pose both important bio-logical and clinical management questions. Smokers cured of one aerodigestive cancer, including lung can-cer, are at greatly increased risk of developing a second primar