ERBB2 and breast neoplasm: They also found that SHP-1 expression correlated directly with expression of HER2 (11% and 18% SHP-1 positive rates in HER2 immunohistochemical staining 2+ and 3+ samples, respectively) and inversely with expression of the estrogen receptor (13% versus 5% in estrogen receptor-negative and positive samples, respectively) and concluded that SHP-1 expression was confined to a well-defined subset of high-grade breast tumors [41].