Why whales don't seem to get cancer
Cetaceans were not limited by gravity in the buoyant marine environment and evolved multiple giant forms, exemplified today by the largest animal that has ever lived: the blue whale (Balaenoptera musculus).
There are tradeoffs, however, associated with large body size, including a higher lifetime risk of cancer due to a greater number of somatic cell divisions over time. The largest whales can have ∼1,000 times more cells than a human, with long lifespans, leaving them theoretically susceptible to cancer.