Recurrent EML4–ALK-associated lung adenocarcinoma with a slow clinical course

The fusion gene EML4–ALK (echinoderm microtubule-associated protein-like 4 gene and the anaplastic lymphoma kinase gene) was recently identified as a novel genetic alteration in non-small-cell lung cancer. The clinicopathological features of EML4–ALK-positive adenocarcinoma are reported to include its high incidence in young, non-smoking patients, tumors that show distinct solid or acinar growth patterns with or without signet-ring cell histology, and its mutually exclusive occurrence with mutations in EGFR and KRAS. However, the clinical findings have not been well described. Here, we report a case of EML4–ALK-positive lung adenocarcinoma that showed multiple metachronous lesions on the pleura and pulmonary field, suspected to be a recurrence of lung adenocarcinoma after a 20-year disease-free interval. The slow clinical course may be characteristic of EML4–ALK-positive lung adenocarcinoma. Therefore, long-term observation of patients with EML4–ALK-positive lung adenocarcinomas is required after surgery.