Sharks get cancer plenty, despite a myth that made it into supplement aisles
A 1992 bestseller claiming sharks were virtually immune to cancer helped launch a worldwide shark-cartilage supplement industry. A cancer registry of shark and ray tumours, along with a 2004 study, documented dozens of naturally occurring shark cancers, including in the cartilage itself, and found no evidence cartilage extracts treat human cancer. Sharks are just understudied, not immune.