The use of IHC staining of tissue samples to guide targeted treatment is widely used in clinical practice, and is recommended by expert groups for many tumor types and biomarkers. [11,12] The classical approach to IHC scoring for biomarkers, such as human epidermal growth factor receptor-2 (HER2), classifies specimens as either ‘positive’ or ‘negative’, scoring samples as IHC0, 1+, 2+ or 3+ per pathologists’ visual interpretation. [11,12]