Assessing HER2 amplification by IHC, FISH, and real-time polymerase chain reaction analysis (real-time PCR) following LCM in formalin-fixed paraffin embedded tissue from 40 women with ovarian cancer

We compare HER2 receptor amplification analysis by immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and real‐time polymerase chain reaction (real‐time PCR) DNA copy‐number assay following laser capture microdissection (LCM) in formalin‐fixed paraffin embedded tissue from 40 women with verified ovarian cancer. We speculate that LCM should result in a more accurate assessment of HER2 amplification in our real‐time PCR assay compared with IHC and FISH. HER2 overexpression measured by IHC, FISH, or real‐time PCR was found in 5.0%, 5.0%, and 22.5%, respectively. HER2 negative results measured by IHC, FISH, or real‐time PCR were found in 95%, 92.5%, and 60.0%, respectively. Analysis failed for IHC, FISH, or real‐time PCR in 0%, 2.5%, or 17.5% of cases. Concordance between IHC and FISH, IHC and real‐time PCR, or FISH and real‐time PCR were 89.7%, 72.7%, or 78.1%, respectively. Only few ovarian cancer patients were HER2 overexpressed measured by IHC or FISH and thus could be eligible for antibody‐based therapy with trastuzumab (Herceptin). Interestingly, we find an increased number of HER2 positive patients by real‐time PCR analysis on microdissected cancer cells, suggesting a number of HER2 positive patients not detected by current methods. Thus, the concept of quantitative measurement of HER2 on microdissected cancer cells should be explored further.