Kurzgesagt - In a Nutshell (2013) : 8x3

Cancer is a creepy and mysterious thing. While we tried to understand it, to get better at killing it, we discovered a biological paradox that remains unsolved to this day: large animals seem to be immune to cancer. Which doesn’t make any sense – the bigger a being, the more cancer it should have. To understand why, we first need to take a look at the nature of cancer itself.