The c-ros oncogene 1 (ROS1), originally described in Glioblastomas, has been identified as a potential relevant therapeutic target in lung Adenocarcinoma. Crizotinib has shown in vitro activity and early evidence of clinical activity in ROS1-rearranged tumors. FISH is better-suited than molecular testing to detect the spectrum of variants of ROS1 gene. It has seven chromosomes described so far in Non-Small Cell Lung Carcinoma (NSCLC). While molecular assays must be designed to individual and unique fusions, FISH detection encompasses all described and as-yet undescribed rearrangements.