ERBB2 and ovarian cancer: Figure 3A presents the representative images of HER2 IHC ranging from HER2 0 to 3+. PDTX 18-4 showed HER2 3+, that is HER2-overexpressing, WJO-002 showed HER2 2+, that is HER2-equivocal, and WJO-004 and CPDX-005 showed HER2 1+/0, that is HER2-negative (Figure 3A). We further performed the silver in situ hybridization (SISH) to identify HER2-equivocal PDTX cases with HER2 gene amplification. WJO-002 and PDTX 39-1 did not amplify the HER2 gene. Figure 3B presents a summary of the level of HER2 expression in eight ovarian cancer PDTX models.