Objective: Lung cancer is the carcinoma with the highest mortality and incidence. Genetic factors that cause lung cancer are the oncogenes and tumor suppressor genes underlying carcinogenesis. ALK gene is a transmembrane protein with tyrosine kinase activity. Because of inversion of ALK gene with EML4 gene, the EML4-ALK complex occurs. The EML4-ALK complex is continuously active, resulting in continuous cell proliferation. FISH is known as the "gold standard'' method to detect the EML4-ALK fusion gene, which is mostly seen in adenocarcinoma. In our study, we aimed to underlie the outcomes of detection of EML4-ALK gene rearrangement in clinics.