Common primary tumors that may spread to the liver include gastrointestinal cancers (such as colorectal, pancreatic, stomach and esophageal), as well as breast cancer, lung cancer, melanoma, and a number of other cancers. The reasons for such spread vary, and depend both on blood flow and on the characteristics of the different cancer cells. For example, cancers of the gastrointestinal tract often spread to the liver because blood flows directly from these organs to the liver. Cancer cells, therefore, have a direct path to the liver. Alternatively, melanoma usually spreads through the body's arteries to the liver. The risk of cancer spreading to the liver depends on the primary cancer site. Liver metastases may be present at the time the primary cancer is diagnosed, or they may occur months or years after the primary tumor is removed.
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