ABC News reports on dogs who can identify cancer by sniffing, starting out with the story of Carolyn Withers, who claims that her Labrador retriever started jumping on her right breast and barking. She did a breast self-exam and found a lump. She had surgery and is now fine. Coincidence?

In one study cited in the report, dogs were trained to sniff different urine samples and distinguish between those from people with bladder cancer and control sample. Other studies have shown that dogs can distinguish between breath samples of those with lung or breast cancer and controls. Researchers are now trying to figure out what exactly the dogs are smelling to come up with more precise tests.

Harvey Pass, head of thoracic surgery at NYU Medical Center, thinks that dog-sniffing clinics might just happen one day. "Could you imagine you have the early detection clinic that's in a given area of the hospital, that people would come, and then they'd go into a room and there's a series of dogs, that then look at them and they either lie down, or they sit up, and just that signal may tell you what's going on. I wouldn't bet against it."