The algorithm then determines the intensity (strong, moderate, weak) and pattern of staining (circumferential versus partial) around each invasive cancer cell to provide a breakdown of the percentage of cells in each HER2 category—0, 1+, 2+, 3+ —and on the basis of these percentages assigns an overall HER2 score using the ASCO/CAP criteria (Figure 3). Here, ERBB2 is linked to cancer.