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Invasive Cancer
Invasive cancer is defined as cancer that has spread beyond the layer of tissue in which it originated developed and is growing into surrounding healthy tissues (1). It is also known as "infiltrating cancer" (2).
There are three main ways that cancer can spread: locally, through the circulatory system, and through the lymphatic system (2). The term "invasive cancer" usually refers to cancer traveling through the body locally, which means that it spreads in a direct path from the original site of the cancer to a nearby site.
The spread of cancer from one area to another is not fully understood by the medical community, but research suggests that three main factors are involved: pressure, enzymes, and the movement of the individual cancer cells. By growing beyond the size allowed by the tissue that contains it, tumors utilize the resulting pressure to press through any barriers (such as sheets of muscle), gaining access to new areas in which it can spread. As it grows, it squeezes and blocks blood vessels which supply vital blood and oxygen to the region, which causes some of the healthy tissue to die off. This allows the tumor easier passage through the tissue, enabling it to spread more quickly. At the same time, it is believed that cancer cells produce various enzymes that help break down the healthy tissue, further easing its path. Finally, individual cancer cells move more freely than cells in healthy tissue, which generally stick together. In fact, it has been discovered that cancer cells produce a substance that stimulates them to move from the tumor to new areas. By traveling on an individual basis, the malignant cells can establish themselves in nearby tissue (2).
- National Cancer Institute's Dictionary of Cancer Terms. Available: "Invasive Cancer." (Accessed July 18, 2007).
- Cancer Research UK's website. Available: "How Cancer Grows Locally." (Accessed July 18, 2007).