Colleen Ferguson with her dog Inca who alerted her to a tumour in her lung. A woman says she owes her life to her pet dog which sniffed out the early stages of lung cancer. See MASONS story MNSNIFF. Teacher Colleen Ferguson, 60, was puzzled when German shepherd Inca started sniffing her breath. Non-smoker Mrs Ferguson said she had no symptoms of any illness apart from recently feeling tired. But she followed her dog's instinct and went for a private health check and weeks later was given the devastating news that scans had found a golf-ball-sized tumour in her left lung. A biopsy confirmed the tumour was cancerous and Colleen went to Guy's Hospital in London where she had the lump and half her lung removed earlier this month. Less than two months after her diagnosis, she is recovering well at home in Headcorn, Kent and hopes to receive confirmation she is cancer free soon.