EGFR and cancer: The proposed result is a constitutively active tethered EGFR-ERBB4 kinase (Fig 3C).15-17 In publicly available cancer databases, ERBB4 fusions are rare but recurrent, comprising approximately 0.1% of ERBB family fusions, primarily in ovarian, breast, and lung carcinomas.17 More rare are ERBB4 fusions with proposed tethered kinase activation.