Is cancer contagious if someone received blood from a patient with stage 4 cancer with metastasis to the blood?

No, cancer is not contagious. Receiving blood from someone with cancer does not put you at risk for contracting the disease. However, some blood-borne illnesses can be spread through transfusions, such as HIV and hepatitis B and C. These viruses are screened for in donated blood to reduce the risk of transmission. In addition, even if someone has stage 4 cancer with metastasis to the blood (which means it has spread throughout their body), this still does not make the disease itself contagious; only a few viral cancers (Hepatitis B and C) can actually be transmitted from person to person via contact or bodily fluids like saliva or semen. So while receiving a donation of blood from an individual with cancer may pose an increased risk of transmitting certain infectious diseases, it will never directly expose you to any form of cancer itself.