My father-in-law was found to have a tumor on his pancreas. Usually, I am in good health, and I have not seen any symptoms such as emaciation and yellow skin. Can this still be cancer?

According to your description, your father-in-law is likely to have pancreatic cancer, but further diagnosis is needed. Yellowing of the skin is probably caused by jaundice, and emaciation and fatigue are also likely due to pancreatic lesions. Because the pancreas is one of the important digestive organs of human body, once it gets sick, it will cause emaciation and fatigue. So I suggest you take your father-in-law to the hospital for examination as soon as possible so as to make a diagnosis of this series of diseases.