ERBB2 and breast cancer: In these guidelines, the final score is 0, 1+, 2+, or 3+ based on membrane staining, among which scores of 0/1+ and 3+ are considered to be negative and positive for HER2 OE, respectively; a score of 2+ is considered equivocal and should be confirmed by additional in situ hybridization (ISH) testing in BC.