ERBB4 and non-small cell lung carcinoma: The identification of activating somatic kinase domain mutations in the human epidermal growth factor (HER) or the human erythroblastoma virus B (ErbB) family of trans-membrane receptors, which consists of the four homologous members EGFR (HER1; ErbB1), HER2 (ErbB2), HER3 (ErbB3) and HER4 (ErbB4), has enabled major advancement in the treatment of non-small cell lung cancer (NSCLC) [1, 2].