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.
Two hypotheses may explain the progression to two tumor types: (1) atypical ductal hyperplasia (ADH) is a precursor of ductal carcinoma in situ (DCIS), which is a precursor of invasive ductal carcinoma (IDC); or (2) ADH is a precursor of HER2-negative IDC whereas DCIS is a precursor of HER2-positive IDC.
We and others have determined that c-erbB-2 is substantially expressed in most ductal in situ carcinomas of the comedo type, but not in other patterns of ductal carcinoma in situ or in atypical ductal hyperplasia of the breast.