Scientists found the fourth type of transmissible cancer, and the first in a fish: a melanoma whose tumor cells spread between catfish in a Vermont lake.

For more than a decade, there's been something fishy going on in a lake that straddles Vermont and the province of Quebec. It involves cancer, a kind of catfish, and — possibly —…

Transmissible tumours have been found in only a few types of animal, but there might be many more out there.