ERBB4 and thyroid cancer: In addition, in clinical immunohistochemical study, we also investigated the expression of HB-EGF proteins and its receptors, HER1 and HER4, in human thyroid cancer tissues, suggesting that a novel role of HB-EGF-induced chemotaxis might be mediated by tyrosine phosphorylation not only of HER1 but also of HER4 in the thyroid cancer cells.