ERBB2 and breast cancer: QASeq was applied to 18 fresh/frozen (FF) tumor samples from 16 breast cancer patients and was compared with both ddPCR and immunohistochemistry (IHC) results on ERBB2. QASeq ERBB2 ploidy results were concordant with IHC and ddPCR from the tumor tissue (Fig. 2c, d) with potentially fewer false positives.