Single-day HER2neu amplification assessment using chip-based digital PCR in formalin-fixed paraffin-embedded breast carcinoma tissue

Human epidermal growth factor receptor 2 (HER2) amplification is present in almost 15%-20% of breast cancer tumors, making it an important parameter for testing. The present study was designed to evaluate a chip-based digital PCR (dPCR) system for assessing HER2 amplification from formalin-fixed paraffin-embedded breast carcinoma tissue and to compare this system with immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). A total of 84 breast carcinoma tissue samples were analyzed by IHC, FISH, and chip-based dPCR in a blinded manner. All nine IHC-positive and 35 IHC-negative samples had equivalent results with dPCR, taking an amplification ratio threshold of 1.8 as a positive result. Of the 40 IHC equivocal samples, 10 were assessed as positive, 27 as negative, and three as equivocal by dPCR. These results demonstrate that chip-based dPCR is suitable for HER2 amplification detection in formalin-fixed paraffin-embedded samples in a clinical setting, providing the advantages of superior turnaround time, cost-effectiveness, and increased precision with absolute quantification compared with conventional tests such as FISH and IHC. This methodology was especially beneficial in tissue samples with low DNA concentration.