Dogs have an amazing sense of smell thanks to 300million smell receptors in their noses, compared to only five million in the human nose. Medical dogs are trained by smelling samples of people already diagnosed with cancer and those of people without the disease so they can learn to tell the difference. Dr Claire Guest began training her dog Daisy to smell out the killer disease in urine  and breath samples  when she was young. So far Daisy has found cancer in 551 patients, of which 93 per cent were accurate. And she discovered Dr Guest's breast cancer before it was diagnosed- the first time she has discovered the disease actually growing in someone's body, rather than by smelling a sample. Dr Guest, 50, chief executive of charity Medical Detection Dogs, said: "She pushed against my body with her nose repeatedly - I pushed her away, but she pushed against me again, clearly upset. She pushed me so hard that it hurt me.  "Her behaviour was totally out of character - she was normally such a happy dog ... I felt the tender area where she'd pushed me, and over the next few days I discovered the tiniest lump . "If it wasn't for Daisy it would have gone hidden for much longer and could have been more serious," Dr Guest added. "My own pet labrador saved my life." Animal rescue charity Blue Cross presented Daisy with a medal for her achievements. She faced tough competition, including JJ, a bomb detection dog who has saved soldiers' lives in Afghanistan. Steve Goody, the charity's deputy chief executive, said: "Cancer affects the lives of thousands of people and Daisy has made a huge contribution to the diagnosis and early treatment of cancers - she's a very deserving medal _ t." Daisy is now helping to train a team of 12 dogs at Medical Detection Dogs and is a 'senior consultant' for the UK's first ever trial using dogs to discover breast cancer. How did Daisy discover Dr Guest's cancer?
By smelling the urine sample. By smelling the breath sample. By smelling the hidden cancer. By pushing Dr Guest hard.