ALK and lung adenocarcinoma: Despite the initial poor performances of ALK on lung adenocarcinoma, immunohistochemistry is currently considered reliable and cheap, due to employment of signal amplification system and optimized anti-ALK antibodies, such as clone 5A4 (Novocastra) or D5F3 (Ventana), with the latter being approved by FDA (Food and Drug Administration) as companion diagnostic test for ALK rearrangements [6].