ERBB2 and cancer: Unsurprisingly, greater than 85% of primary UC tumors demonstrated phosphorylation of EGFR (100%) and ErbB2 (89%) which is concordant with prior studies suggesting that overexpression of ErbB2 and EGFR is a common event in this cancer [22, 23] and that alterations in ErbB2-mediatied [24] signaling pathways drive the proliferative phenotype in UC cells.