Objective: To introduce the College of American Pathologists/American College of Medical Genetics Cytogenetics Resource Committee criteria for genetic heterogeneity (GH) in HER2 testing, and investigate the clinicopathological significance of HER2 genetic heterogeneity in invasive breast cancer.
Methods: The clinical parameters of 100 cases of invasive breast carcinomas were collected. HER2 expression level and HER2 gene copy number in formalin-fixed and paraffin embedded tumor samples were detected by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), and the relationship between HER2 gene GH and clinicopathological characteristics were analyzed.
Results: Among the 100 patients, HER2 gene GH was observed in 20 (20%) cases. When the number of HER2 amplified cells was more than 25%, the frequencies of FISH positive were higher than those cases with less than 25% HER2 amplified cells. The results showed that HER2 gene GH was associated with the degree of HER2 protein expression (P=0.004), and ER expression (P=0.002).
Conclusion: HER2 gene GH may be correlated with the HER2 protein IHC 1+/2+, and ER expression in breast carcinoma. It is important for doctors to avoid ignoring or only counting FISH positive cells leading to incorrect diagnosis for these patients.