ERBB2 and neoplasm: HER2 overexpression is scored according to the pattern of membranous staining and percentage of stained tumor cells as follows: 0, no staining or faint incomplete staining in < 10% of cells; 1, faint incomplete staining in > 10% of cells; 2, weak to moderate complete staining in > 10% of cells; and 3, strong complete staining in > 10% of cells.