When nine-year-old Hannah Baker complained of pains in her leg, her parents and GP initially put it down to growing pains or a pulled muscle.
But when the pain did not subside after two weeks, and Hannah had an x-ray, her family were given the shocking news that she had a 22cm tumour on her femur.
Her mum, Shim, 36, says that if the tumour had not been caught when it was, Hannah could have died.
"Hannah had been doing lots of sports and complained that her leg was aching," says Shim. "She didn't compete in the school cross country and I noticed as she walked back from watching it, she was moving strangely. I picked her up to put her in my lap and she screamed."
Shim took Hannah to see their GP who gave her pain killers, but ordered an x-ray two weeks later when Hannah was still in terrible pain.
"Three hours later Hannah and I were told they had found a tumour," says Shim. "In two weeks we had gone from having a healthy little girl to her having cancer."
The devastated mum says she was left 'numb and speechless' by the diagnosis:
"We thought we're going to wake up in a minute from all this but we just had to stay strong and be there for each other."
Hannah underwent four weeks of chemotherapy, but still faced losing the limb until surgeons at the Royal Orthopedic Hospital, Birmingham, carried out an operation to insert a titanium rod on her femur which will grow as she gets older.
Hannah is now on the road to recovery after a grueling six months of intensive surgery and further chemotherapy.
The plucky schoolgirl says she cannot wait to be fully recovered and swimming and playing sports again.
Her relieved Dad Paul told the Daily Mail that he was hopeful Hannah would soon get the all-clear.
"It was likely she was born with the cancer and it lay dormant, and her growth spurts as she got older as a child triggered the bone cancer," he said. "The tumour was 100 per cent removed and 100 per cent dead but the chemotherapy will continue until Christmas when hopefully she will be given the all clear."
Brave Hannah - who managed to visit her school just four weeks after her surgery - has donated her cancerous femur to science.
"She's a very determined young lady," her dad said.