Why whales don't get cancer
Cancer should be a near certainty for whales, being the longest-living and largest mammals there are. Across species, the higher the number of cells, the greater the number of cell divisions and the higher the probability of DNA damage and the transformation of a normal cell into a cancerous one.
However, the occurrence of cancer does not show a correlation with body mass. The lack of correlation between body mass and cancer risk is known as Peto’s paradox.