ERBB4 and neoplasm: NRG2 has moderate affinity with ERBB2/4 heterodimers, and phosphorylation of ERBB2/3/4 may serve as an alternative biomarker for pathway activation.33Immunohistochemical analysis of CD74-NRG2 samples showed moderate phosphorylation of ERBB4 in positive tumor cells, whereas EGFR, ERBB2, and ERBB3 did not show phosphorylation.