Can dogs sense various degrees of cancer and illness?

Yes, in fact, all animals including humans have the ability to sense lots of things like this. Dr. Fritz Albert Popp, a German radiology teacher discovered some quite incredible things about all living things and used quantum physics experiments to prove up these discoveries.

He discovered and photographed with very sophisticated equipment, cells emitting light, storing light, and using light to communicate from one organism to another and cells within the organism communicating with each other. This he believes is the way schools of fish all turn simultaneously as one example. There was a Japanese researcher working with the Cancer Institute in New York that developed a way to sense cancer cells in organisms by using the biofield. He could put known cancer cells near a patient and if the body had these cells in them, the biofield would react differently than if no cancer were in the body.

Since animals are more "pure" in the aspect of sensory perception it seems than humans, it makes sense that dogs could sense these things.

good luck to you

There may be some dogs who have the ability to smell cancer . . but certainly not all dogs. There are efforts underway to train dogs with smell sensitivity to try and detect cancer in humans. But, no, not all dogs can pick up the scent. Therapy dogs are well trained and around those with disease so what you are seeing is a well trained animal who may also have some type of sensitivity to humans with disease. We had three poodles (two standards and one mini) and they never reacted one way or the other to my sons cancer even though one of the poodles was his dog. Still love the dogs though.