Abstract 45P
Background
Breast cancer (BC) highly correlates with cancer-associated death and female malignancy. About 20% of BC patients are human epidermal growth factor receptor 2 (HER2) positive; they also show significant response to Herceptin treatment. Despite advances in treatment and the prognosis in early detection and diagnosis, HER2-positive BC remains lethal and has increased in mortality rate. One potential cause might be the misdiagnoses of HER2 status evaluation, which negatively impacts clinical decision-making. The common approach for HER2 diagnosis is utilizing immunohistochemistry (IHC) to detect the expression level from the upper-cut tissue section of each tumor block. Yet HER2 expression may show discrepancy in the tumor block. Here we apply anti-HER2 antibody in IHC to detect HER2 expression in lower, middle, and upper cuts of human BC tissue sections from the same block to find out possible discrepancies and inconsistencies in HER2 expression level.
Methods
To compare and assess the HER2 expression by IHC, we first obtained human BC tissue blocks from Tzu Chi Hospital (Hualien, Taiwan) and cut out 20 5μm tissue sections from each block. Then we picked up the topmost, middle, and the bottom sections for HER2 expression analysis. HercepTestTM kit (Dako, A0452) was applied to each selected slide according to the manufacturer’s protocols. Finally, staining results were evaluated using the criteria 0, 1+, 2+, and 3+ according to the kit instructions, which were the standardized criteria at the time.
Results
Although most of the IHC results showed no difference between the lower and upper cuts of breast cancer blocks, there indeed existed some patients with distinct expression levels of HER2 in different cuts from the same tissue block. 4 blocks out of 27 showed opposite HER2 staining results on the topmost, middle, and the bottom sections.
Conclusions
In this study, we illustrated that the expression of HER2 is distributed unevenly in the tumor blocks. Our results suggested that using only one cut of each breast cancer block to represent the whole HER2 expression in tumor for diagnosis may cause come dispute. A more consummate and efficient approach to detect the level of diagnostic markers in the whole tumor is urgently needed.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Ministry of Science and Technology, Taiwan, R.O.C.
Disclosure
All authors have declared no conflicts of interest.