Mechanisms of progression of ductal carcinoma in situ of the breast to invasive cancer

Ductal carcinoma in situ (DCIS), a known precursor lesion of invasive cancer of the female breast, is surrounded by a thick basement membrane and a layer of myoepithelial cells. For DCIS to become invasive, both these barriers must be breached by cancer cells. It has been repeatedly suggested that proteolytic enzymes are somehow involved in this process but a direct proof of this event has never been provided. It is our hypothesis that invasion of the DCIS by capillary vessels derived from the periductal necklace of vessels is the most likely mechanism of breaching the basement membrane, providing an escape hatch for cancer cells.