Fiset PO, Labbé C, Young K, et al. - Given that response to anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor therapy is predicted by ALK rearrangement, therefore, researchers focused on the utility of ALK immunohistochemistry (IHC) assays, using ALK antibodies other than D5F3, as diagnostic tests for ALK rearrangement. They analyzed data from reflexive clinical ALK IHC test using the 5A4 clone combined with epidermal growth factor receptor (EGFR) mutation testing. Findings are suggestive of a robust ability of ALK 5A4 IHC to serve as a diagnostic test for ALK-rearranged lung cancer. Also, ALK 5A4 IHC was found to be related to treatment response and survival. Combined reflex EGFR and ALK testing offered high success rates; this occurred due to optimized tissue allocation.