Proliferative lesions of the breast: carcinoma in situ.

Many breast carcinomas probably arise in a multi-step fashion through a series of intermediate lesions viz. ductal hyperplasia to atypical ductal hyperplasias to ductal carcinoma in situ (DCIS), and thence to invasive ductal cancer, each of which has a greater probability of becoming malignant than the one that preceded it. These precursor lesions have differing risk implications, hence treatment decisions vary with the risk. The heterogeneous lesions that come under the heading of hyperplasias and DCIS can cause problems for the histopathologists unless there is a conceptual understanding of the disease process. Since the surgical pathology report is the final word in cases of DCIS/LCIS, the pathologist becomes a vital partner in the decision making team.