Metastatic Carcinoma in Lung Tissue at 10x Magnification
The tumors that are most likely to metastasize to the lungs are those that exhibit a well-developed vasculature. Indeed, angiogenesis (the development of capillaries) is considered one of the primary steps any tumor takes on its way to becoming dangerously malignant. Investigations of this process are ongoing, but it appears that some cancer cells are able to aggregate existing proteins in the body that facilitate angiogenesis and eventually develop to the point where they are capable of synthesizing such proteins themselves. One of these proteins facilitates the invasion of a tumor by endothelial cells. These cells accumulate and multiply to form capillaries, which are thought to promote tumor growth and cancer cell mobility.