HER2 testing in gastric cancer: An update

Figure 1 Human epidermal growth factor receptor 2 testing algorithm. HER2: Human epidermal growth factor receptor 2; IHC: Immunohistochemistry; FISH: Fluorescent in situ hybridization; CEP17: Chromosome 17.

Figure 2 Human epidermal growth factor receptor 2 expression in gastric and breast tumors. A: A HER2-positive (3+) case of gastric adenocarcinoma; the cytoplasmic membranous immunostaining is incomplete and predominantly basolateral (× 400); B: A HER2-positive (3+) case of invasive ductal carcinoma of the breast; the cytoplasmic membranous staining is fully circumferential (× 400). HER2: Human epidermal growth factor receptor 2.

Figure 3 Representative image of the intratumoral heterogeneity of HER2 expression. Arrows indicate areas with strong continuous membranous staining (score 3+) and arrowheads indicate negative areas (score 0) (× 100). HER2: Human epidermal growth factor receptor 2.

Figure 4 Human epidermal growth factor receptor 2 protein expression in gastric and gastroesophageal tumors. A: A negative (0) case; B: A negative (+1) case; C: An equivocal (2+) case; D: A positive (3+) case. HER2: Human epidermal growth factor receptor 2.