Although it is a rare occurrence, cancer can spread from one creature to another. In the past, this phenomenon had only been found in tasmanian devils, dogs, and clams. However, after conducting a gene sequence of marine creatures known as bivalves, researchers found that cancer can be contagious between other species of mollusks. They have also found evidence ofcross-species transmission among the bivalve class of sea-life. Scientists are quick to point out that this is not a reason to stop eating your favorite seafood dishes. It is their strong belief that this contagion only happens between shellfish, and is not transmissible to humans. Source