ERBB2 is overexpressed in approximately 15–20% of breast, gastric, and oesophageal human cancers as a result of amplification of the ERBB2 gene, and this is a prognostic biomarker as “HER2 positive” tumours (which show ERBB2 gene amplification) typically show a faster growth rate and more aggressive clinical behaviour [188]. The gene discussed is ERBB2; the disease is neoplasm.