Possible Prognostic Role of HER2/Neu in Ductal Carcinoma In Situ and Atypical Ductal Proliferative Lesions of the Breast.

HER2/neu is a well-established prognostic and predictive factor for invasive breast cancer. However, the role of HER2/neu in ductal breast carcinoma in situ (DCIS) is debated and recent data have suggested that it is mainly linked to in situ local recurrence. Although molecular data suggest that atypical ductal hyperplasia (ADH) and duct carcinoma in situ (DCIS) are related lesions, albeit with vastly different clinical implications, the role of HER2/neu expression in atypical ductal hyperplasia is not well defined either. The aim of this study was to evaluate over expression of HER2/neu in DCIS and cases of ADH in comparison with invasive breast carcinoma. Archival primary breast carcinoma paraffin blocks (n=15), DCIS only (n=10) and ductal epithelial hyperplasia and other breast benign lesions (n=25) were analyzed for HER2/neu immunoexpression. Follow up was available for 40% of the patients. HER2/neu was positive in 80%of both DCIS and invasive carcinoma, and 67% of atypical ductal hyperplasia (ADH) cases. Thus at least a subset of patients with preinvasive breast lesions were positive, which strongly suggests a role for Her2/neu in identifying high-risk patients for malignant transformation. Although these are preliminary data, which need further studies of gene amplification within these patients as well as a larger patient cohort with longer periods of follow up, they support the implementation of routine Her2/neu testing in patients diagnosed as pure DCIS and in florid ADH.