Patients with non-small cell lung cancer (NSCLC) who harbor anaplastic lymphoma 
kinase (ALK) gene rearrangements can derive significant clinical benefit from 
ALK tyrosine kinase inhibitor. Accurate patient identification is absolutely 
crucial for successful using ALK inhibitor treatment. However, lung cancer 
patients with ALK gene rearrangement after ALK inhibitor therapy eventually 
develop acquired resistance to treatment. In this review, the authors summarize 
the clinicopathologic features of ALK-rearranged NSCLC and the pros and cons of 
current diagnostic testing. In addition, we discuss the current diagnostic flow 
of ALK testing and consideration of rebiopsy sample during disease progression 
in patients treated by ALK inhibitors.