EML4-ALK positive lung cancer is a primary malignant lung tumor whose cells contain a characteristic abnormal configuration of DNA wherein the echinoderm microtubule-associated protein-like 4 (EML4) gene is fused to the anaplastic lymphoma kinase (ALK) gene. This abnormal gene fusion leads to the production of a protein that appears, in many cases, to promote and maintain the malignant behavior of the cancer cells. The transforming EML4-ALK fusion gene was first reported in non-small cell lung carcinoma (NSCLC) in 2007.