Olivia Maunder, 15, was later diagnosed with Ewing Sarcoma – a rare form of the disease affecting the bones and surrounding tissue – and now has just months to live.

Staff at Frimley Park Hospital, in Camberley, Surrey, initially missed the tumour in Olivia's pelvis when she had an MRI scan in March 2021.

Instead, doctors diagnosed her with complex regional pain syndrome (CRPS), a little-known condition often thought to be caused by the body reacting abnormally to an injury.

Over the following three months the teenager endured 'indescribable agony' and was taken to A&E on multiple occasions.

But Olivia, from Bordon, Hampshire, said she was offered little help from staff and at one point was told to 'calm down'.

She added: 'I was even told that I was mirroring my mum's pain as she had had back problems. I wasn't being treated at all, I just existed in pain.'

Olivia's mother, Carol Rolfe, 52, said: 'We told the doctors so many times how much pain she was in.

'She was screaming in pain, but we were asked, 'Have you tried a mindfulness app?' and were told it was stress. They wanted her to be quiet and not disturb others.'

Olivia initially felt 'relieved' after receiving the CRPS diagnosis – but then became frustrated when she was given no pain medication.

'I knew that I was in pain and that this wasn't in my head,' she said.

The teenager and her family began to question the CRPS diagnosis further when her pain continued to increase over time.

And a second MRI was arranged only after her mother spoke to an expert on the condition.

Only at this point was the tumour discovered but by then it was so extensive that surgery was no longer an option.

A serious incident report carried out after the missed diagnosis at the hospital later revealed significant failings in her care.

Olivia first began to feel 'niggles' in her back in 2020 but she didn't see a GP until January 2021, after the pains worsened over the Christmas period.

After months of painful chemotherapy and radiotherapy, Olivia was able to go back to school in April 2022.

However, her condition has since deteriorated and she was recently told she has months to live.

'When the doctors said they had found a tumour in my pelvis it felt like an out of body experience. I was in shock,' she said.

'Afterwards I was extremely angry. They told me I had a tumour three months after they said I was making it all up and had been suffering terribly.'

The family have now instructed solicitors Devonshires Claims to take legal action against Frimley Park Hospital Trust.

Jeanette Van-Cauter, a specialist medical negligence lawyer from the law firm, said: 'Olivia is one of the bravest young people I have met, and her story is one of the most tragic... this is unacceptable and I believe that those responsible should be held to account.'

Frimley Health NHS Foundation Trust medical director Dr Timothy Ho said: 'We are very sorry for the considerable distress caused by the delay in diagnosing Olivia's cancer and have met with Olivia and her family to share the results of our thorough investigation.

'We are committed to learning from the investigation and improving services and will support Olivia and her family as best we can at this difficult time.'