Sharks are not immune to cancer
A widespread myth claims sharks never get cancer, a belief that led to the overharvesting of sharks for ineffective health supplements. In truth, scientists have documented cancer in more than twenty species of sharks, including tumors found directly in their cartilage. Sharks do get cancer—they just rarely suffer from some specific human diseases.
The Rise of a Persistent Myth
For decades, an enduring belief circulated in popular culture and alternative medicine markets: the idea that sharks are completely immune to cancer. This claim gained widespread traction in the late twentieth century, popularized by books and commercial marketing that positioned shark tissue as a biological miracle. The narrative suggested that because sharks have survived for hundreds of millions of years virtually unchanged, their bodies possessed an impenetrable defense against malignant cell growth.
The premise was simple enough to sound plausible to a general audience. Commercial advocates claimed that sharks possessed unique biological properties that prevented abnormal cells from developing or spreading. This sparked a massive commercial boom in shark cartilage supplements, marketed heavily to desperate patients seeking alternative or complementary cancer therapies. However, this appealing narrative rested on a fundamental misinterpretation of biological research rather than rigorous scientific consensus.
What Marine Pathology Actually Shows
Contrary to the popular claim, sharks do get cancer. Marine biologists, veterinary pathologists, and fisheries scientists have documented both benign and malignant tumors across dozens of shark, skate, and ray species. Pathologists have cataloged cases of cancerous growths affecting various organs and tissues in these cartilaginous fishes, including the liver, blood, skin, and sensory systems.
Perhaps the most direct contradiction of the supplement industry's claims is that tumors have been identified directly within shark cartilage itself. Conditions such as chondromas and chondrosarcomas—tumors arising in cartilaginous tissue—demonstrate that cartilage offers no absolute barrier to cellular malfunction. While documenting wildlife diseases in open-ocean animals presents logistical challenges, the existing scientific records leave no doubt that the Chondrichthyes class is susceptible to neoplastic disease.