Can man's best friend be trained to sniff out a dangerous health condition? Carolyn Withers is convinced the answer is yes.

Withers said her dog, Myles, was not afraid to speak up when he thought something was wrong. He did it over and over again to her, reported WCAU-TV in Philadelphia.

"He would jump up and forcefully put his nose right into my arm area, and he would be flipping my arm up, and he would jab me toward my breast and underneath my arm," Withers said. "Then he would bark and bark in a frantic-sounding way."

After six weeks of this routine, Withers began to wonder if something was wrong.

"I started feeling around, and I felt this bead. It felt like a pearl, like a hard pearl, and so it alarmed me," Withers said. "A day or so later, I went to have a mammogram and I was diagnosed with breast cancer."

Withers was certain that Myles was trying to tell her something: "Telling me he was alarmed, that I was in danger, that my life was in risk, that he smelled the cancer, absolutely. I have no doubt in my mind that he saved my life," Withers said.

Once Withers had her cancerous lump removed, Myles stopped his routine.

"Immediately after my first biopsy, when they removed it, he stopped," Withers said.

Sound far-fetched? Maybe not.

"Well, it's not the first time it's been observed," said Dr. James Serpell.

In fact, dogs are now being trained to detect cancer.

Serpell is a specialist in animal behavior. He runs the Center on the Interactions of Animals and Society at the University of Pennsylvania School of Veterinary Medicine.

"Their powers of smell are so much vastly better than our own (that) we can't really even imagine the world from their perspective," Serpell said. "That enables them to do things we can't even conceive of.

"So maybe cancer does emit an odor they can smell," he said. "Oh, I think it's quite clear that it does, and perhaps this dog was smelling the cancer. If you can train a dog to smell these differences, there's no reason why a dog couldn't do it spontaneously."