Biology, prognosis and response to therapy of breast carcinomas according to HER2 score

The standardization of the HER2 score and recent changes in therpeutic modalities points to che need for reevaluation of the role in recently diagnosed breast carcinoma. A multicenter, retrospective study of 1794 primary breast carcinoas diagnosed in Italy in 200/2001 and scored in HER2 four categories accordin to immunohistochemistry was conducted. Ductal histotpe, vascular invasion, grade, MIB1 positivity, estrogen and progesterone receptor expression differed significantly in HER2 3+ tumors compared with the other categories. Her2 2+ tumors almost showed values intermediate between those of the negative and the 3+ subgroups. The characteristics of HER2 1+ tumors were found to be in between those of HER2 0 and 2+ tumors. With a median follow-up of 54 months , HER2 3+ status was associated with higher relapse rates in node-positive subgroups, while HER2 2+ only in node positive. Analysis of relapses according to type of therapy provided evidence of responsiveness of HER2-positive tumors to chemotherapy, expecially taxanes. The present prognostic significance of HER2 is correlated to receptor expression level and points to the need to consider HE2+ and HER2 3+ tumors as distinct diseases with different outcomes and specific features.