ERBB4 and cancer: The ERBB family of receptor tyrosine kinases (RTKs), consisting of EGFR (also known as ERBB1, HER1), HER2 (ERBB2, neu), HER3 (ERBB3) and HER4 (ERBB4), were first implicated in cancer in the beginning of the 1980s when it was discovered that EGFR had close sequence homology to avian erythroblastosis tumor virus (AEV) [1, 2].