The most deadly aspect of cancer is its ability to spread, or metastasize. Cancer cells initially group together to form a primary tumor. Once the tumor is formed, cells may begin to break off from this tumor and travel to other parts of the body. This process is metastasis. These cancer cells that travel through the body are capable of establishing new tumors in locations remote from the site of the original disease. Metastasis is a very complicated process that still has yet to be completely understood.
To metastasize, a cancer cell must break away from its tumor, invade either the circulatory or lymph system, which will carry it to a new location, and establish itself in the new site. The body has many safeguards to prevent cells from doing this, yet many cancer cells have the ability to overcome these safeguards. Research is now focused on understanding in what ways cancer cells have mutated to circumvent the body’s defenses and freely travel to other locations.
When cancer is diagnosed, it may be discovered in a site that is not the location of the primary tumor. Through various means of testing, doctors will locate the primary tumor, and determine to what extent it has spread from that location to other areas of the body. Localized tumors that have not had the opportunity or time to metastasize have the best prognosis for cure. Cancers which have metastas