05/18/2026
There is a widespread, persistent myth that sharks are immune to cancer, largely popularized by a 1992 book titled Sharks Don’t Get Cancer by Dr William Lane. The book was used to promote shark cartilage as a cancer treatment, which unfortunately led to a massive spike in the commercial harvesting of sharks and a decline in populations of sharks in some fisheries including Spiny dogfish and hammerhead sharks.
However, marine biologists and veterinary pathologists have definitively proven that sharks do develop both benign and malignant tumors.
The Science Behind It
As early as 1908, scientists have recorded tumors in over 20 different species of sharks, skates, and rays (chondrichthyans). This includes cases of melanoma, carcinomas, and tumors found on their skin, jaws, and internal organs. A notable example occurred in 2013, when researchers on Austraklia’s famed Rodny Fox expeditions photographed a great white shark off the coast of Australia with a large, visible tumor protruding from its mouth.
Sharks have incredibly robust immune systems and a remarkable ability to heal quickly from wounds. Because they are cartilaginous fish, their bodies constantly produce compounds that inhibit angiogenesis (the growth of new blood vessels that tumors need to grow). While this might give them a lower incidence of cancer compared to other animals, it does not mean they are immune.
Ultimately, using shark cartilage does not cure cancer in humans, and perpetuating the myth hurts both human medicine (by steering people away from proven treatments) and ocean conservation efforts.
There is growing concern in the scientific community that rising ocean temperatures, pollution, and exposure to toxic chemicals may be increasing the rates of tumors and other diseases in marine life, including sharks.
In fact, the demand for cartilage to treat inflammation for humans and pets has created a demand that is causing some deepwater sharks and pelagic species like the blue shark to be overfished.