Final answer:
The most likely primary site of cancer that has spread to the liver (liver mets) is another part of the gastrointestinal tract, such as colorectal, pancreatic, ovarian, or breast cancer.
Step-by-step explanation:
When the liver shows mets, it means that there are metastatic cancer cells present in the liver. Metastasis refers to the spread of cancer cells from the primary site to distant locations in the body. In this case, the most likely primary site would be a cancer originating in another part of the gastrointestinal tract. The liver is a common site for metastases from cancers such as colorectal, pancreatic, ovarian, and breast cancer.