Stories about dogs detecting cancer in people abound. These anecdotes are supported by a wealth of research showing that trained dogs can distinguish odors emitted by volatile organic compounds in cancerous cells in the breath, sweat, urine and other bodily fluids. Which is not surprising considering a dog’s sense of smell is 10,000 to 100,000 times sharper than that of a human.

But researchers caution that as long as there’s a risk of false positives, a system must be established to verify and validate these doggy diagnoses.

In addition, some experts, such as Cynthia M. Otto, DVM, PhD, director of the University of Pennsylvania School of Veterinary Medicine’s Working Dog Center, caution that various factors can interfere with a dog’s olfactory sense and throw it off.

Incidentally, it should be noted that no one breed of dog seems better at detecting cancer. Experts say the best canine cancer gumshoes are dogs that are friendly, easygoing and eager to learn.