Progression of Ductal Carcinoma in Situ from the Pathological Perspective

Ductal carcinoma in situ (DCIS) now represents up to 20% of breast cancer cases, yet its behaviour is still poorly understood. Morphological classifications go some way to predicting prognosis, but more sophisticated approaches are required to better tailor therapy to the individual. A number of biological molecules have been identified that appear to relate to prognosis and, in model systems, promote progression to invasive disease. Some of these, such as COX-2, provide real therapeutic opportunities, whilst other marker combinations are showing promise in categorising women according to risk. Gene expression studies have led to an emerging molecular classification of invasive breast cancer, and it is now evident that at least some of these molecular subtypes can be identified at the pre-invasive stage. The difference in frequency of these subtypes between DCIS and invasive cancer may hold clues as to the biological mechanisms underpinning disease transition. It is increasingly clear that the host microenvironment can have a major impact on disease behaviour, and as well as acting as potential predictive factors, the altered microenvironment phenotype also offers novel therapeutic opportunities.