At present, FISH is the preferred cytogenetic method routinely applied e.g., for guiding targeted therapy to identify human epidermal growth factor receptor 2 (HER2) overexpression in breast cancer, human epidermal growth factor receptor 2 anaplastic lymphoma kinase (ALK) rearrangement in adenocarcinoma and BCR/ALB1 translocation in chronic myeloid leukemia [26] and can be applied to detect other gene rearrangements such as ROS proto-oncogene 1 receptor tyrosine kinase (ROS1) [27]. The gene discussed is NTRK1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.