30 July 2012 Last updated at 11:30 ET

Dog 'sniffed out cancer' in her owner's breast

Mrs Rawlinson's husband Brian said Penny was amazing

A woman discovered she had a cancerous tumour in her breast after her dog started sniffing and pawing at it.

Sharon Rawlinson ignored her Cavalier King Charles Spaniel for months, but went for tests after Penny stepped on her chest, causing pain.

Mrs Rawlinson, from Newark, then examined herself and found a lump.

Penny was a surprise Christmas present which her husband almost did not buy, because he said his wife was not allowed to have another dog.

Mrs Rawlinson said 18-month-old Penny was her guardian angel.

"I can't explain how she knew. I just can't get my head around it," she said.

Penny began her unusual behaviour in November, and stepped on her owner's chest in January.

Can dogs detect cancer?

• The first serious suggestion that dogs could "sniff out" cancer appeared in a letter to The Lancet in April 1989
• It contained anecdotal evidence of a dog that kept sniffing a lesion on its owner that was later confirmed as an early malignant melanoma
• A subsequent study by Dr John Church, published in 2004, claimed to prove in principle that dogs could detect bladder cancer in urine
• Further separate studies carried out suggest dogs can also detect lung, bladder and bowel cancer

• Read BBC Health's advice on what to do if you find a lump

Mrs Rawlinson went to her GP and then Nottingham City Hospital for tests, and Penny continued to paw her while she waited for the results.

Mrs Rawlinson began chemotherapy in March and went into hospital for an operation to remove the tumour this week.

"As soon as I started chemotherapy she's not gone near the breast since," Mrs Rawlinson said.

Her husband Brian said the dog was "amazing".

"There's a long, long way to go but at least we've got half a chance," he said.

"If we had left it for any longer, because the tumour was already 33mm, I think we would have had problems."

Martin Ledwick, head information nurse at Cancer Research UK, said: "A few anecdotal cases have suggested that dogs may sometimes be aware that their owner has cancer.

"No reliable research has given a scientific explanation of how this could work."