Ductal carcinoma in situ: current morphological and molecular subtypes

The term ductal carcinoma in situ (DCIS) of the breast encapsulates a biologically, morphologically, clinically and genetically heterogeneous group of lesions. These have a wide spectrum of histological features but are characterized by a non-invasive proliferation of malignant epithelial cells confined to the parenchymal structures of the breast and thus contained within basement membrane-bound structures. Analysis at the molecular and genetic level has improved our understanding of these entities as non-obligate precursors of invasive breast cancer. It is clear that the linear progression model from normal epithelium through hyperplasia to atypical hyperplasia to DCIS to invasive breast cancer is inaccurate. Here we examine current methods for classifying DCIS and some recent molecular advances, including the impact of genetic profiling and immunohistochemistry, upon our understanding of current pathological definitions of DCIS.