The heartbroken mother of a 15-year-old has told of her shock at learning her teenager may succumb to late stage bone cancer, despite suffering virtually no symptoms.

Millie Robinson, from Poole, Dorset, was a perfectly healthy student when, last month, she fell off her bicycle while out cycling with her father.

Soon afterwards she developed a pain in her arm, which the family assumed was a result of the accident. 

But when the sensation intensified, her mother Krista, a 38 year-old carer, decided to take her daughter to A&E.

Doctors performed a series of tests including several X-rays, before sending the pair home.

But later that evening doctors called Ms Dennett to ask her to bring Millie back to the hospital for an emergency MRI. 

After spotting a worrying pattern on the scan, the family were referred to a London hospital for a biopsy that eventually revealed the devastating truth.

Millie was diagnosed with stage four osteosarcoma—bone cancer that has spread to other parts of the body, such as the lungs and other bones.

Healthy and fit Millie Robinson, 15, from Poole, Dorset, was diagnosed with stage four bone cancer after she developed arm pain when she fell off her bike only a few weeks ago in April

But Millie and her mother Krista, 38, insisted there were zero warning signs of the tumor in her arm—which had already spread to her chest at a staggering 11 centimetres. Doctors also suspect there is one in her elbow too

Doctors discovered that the disease had migrated to her chest, and they suspect there is cancer in her elbow too. 

‘I felt absolutely sick, it was the worst day of my life,’ Ms Dennett said of the diagnosis.

‘It’s all just happened so quickly. Our whole world got turned upside down in just a few hours, it’s crazy how much it’s changed our lives.

‘It was a miracle she fell of that bike, the doctors said she would have been dead in six months without treatment.

‘It’s been really tough, but day-to-day you don’t even have time to think about it because it’s all happening so quickly and I have to stay strong for Millie.’

The teenager is now undergoing nearly three months of gruelling chemotherapy before major surgery to remove the tumours, which will be followed by a further four months of radiation treatment.

Speaking of the shock of the diagnosis, Mrs Dennett said: ‘We had absolutely no inkling.

‘Doctors asked her if she had experienced any symptoms like weight loss, headaches or fatigue, but there was nothing to say she wasn’t well.’

Millie had dreams of being an air hostess and travelling the world, but has had to drop out of school to focus on the intensive treatment

Osteosarcoma is rare and one of the deadliest childhood cancers, with an estimated 150 new cases diagnosed in minors in the UK every year.

But long-term survival rates have remained unchanged for over 15 years, with fewer than seven in 10 patients on average surviving beyond five years.

Many of the most typical signs of the disease can mimic common ailments—including pain, swelling, fever, fatigue and weight loss. 

More obvious symptoms include a lump near the infected area, weak or easily broken bones and difficulty moving certain limbs.

Ms Dennett, who has one other child, has had to leave her job in order to look after her daughter full-time.

A GoFundMe page has been set up to help the family with their costs including travel to the hospital an hour away in Southampton and overnight stays.

Millie had dreams of being an air hostess and travelling the world, but has had to drop out of school to focus on the intensive treatment. 

Doctors have given the family hope that the disease could be curable.

‘She’s been so brave and strong, she’s absolutely amazing and still smiling,’ her mother said.