system
Given the following post, respond as if you're commenting on Reddit:
human
Could a blood transfusion spread cancer to another person?

Let's say that a person who didn't know they had a malignant tumour gave a blood donation which happened to contain cancer cells. Ignoring the processes of cleaning and keeping the blood fresh, could it cause cancer if it were transfused into another patient or would white blood cells just destroy it?
gpt
There are cases of transmissible cancers in animals, but these are mostly in highly bottlenecked populations with low genetic diversity (i.e., the cancer is less likely to seem foreign to a new host).

The few cases in humans involve a degree of immunosuppression.

So like the other poster said, it's not impossible, but it's pretty unlikely.