The rationale for this is that in general ISH is considered positive if the ratio of the HER2 gene copy number per tumor cell to the chromosome 17 copy number is greater than or equal to 2 (HER2/CEP17-Ratio ≥ 2) (Summary of Product Characteristics Herceptin® i.v. 2015; Bang et al. 2010) based on a count of at least 20 cells. Here, ERBB2 is linked to neoplasm.