A mum-of-two was given a horrifying diagnosis after believing she had sunstroke.
Janet Sykes assumed her headaches and sense of confusion had been caused by spending too much time in the hot sun.
She started suffering the symptoms after volunteering outside at a village fair in May.
Her painful headaches persisted and she was referred to the Royal Berkshire Hospital, Reading, for an MRI scan. But a week later it revealed a deadly mass on her brain.
The next morning Janet was told the mass was a high-grade glioblastoma multiforme (GBM) and she was unlikely to live for more than five years.
Janet, 44, from Reading, Berks, spoke out as temperatures were set to break UK records and amid a campaign to publicise the symptoms of GMB.
She said: "Hearing this outcome I was in floods of tears.
"I went from thinking I had sunstroke to, a week later, finding out I had terminal brain cancer - I was distraught."
A month after the devastating news, as the country celebrated the Queen's Platinum Jubilee, Janet had debulking surgery at the John Radcliffe Hospital (JR) in Oxford and half of the tumour was removed.
Janet added: "Before I went in to surgery, doctors told me that I could be left with life-changing injuries which is why there is still half the mass on my brain.
"I am currently receiving radiotherapy and chemotherapy to target the remaining cancer.
"So far I am half way through a six-week course of radiotherapy and a week into chemotherapy and I feel well.
"I know that this may change but I am very much of the mind of dealing with my diagnosis one day at a time."
The care worker is expected to finish her treatment in December 2022 and will be monitored with regular scans to check for any regrowth.
Janet and her husband Steve, have been open about her diagnosis with their two children Peter who is eight and David, four.
She said: "Telling the children was hard.
"We took them out of school and spent the day together, as a family and at lunchtime we were honest and had a very tearful conversation with them.
Peter said 'I don't want it to be three of us, I want it to be four,' whereas David asked for a jam sandwich.
"I was given a booklet by one of the nurses with the title 'how to talk to children when an adult has cancer' which Steve and I read through.
"We have done our best to explain that mummy will have a scar and stitches on her head and when I have radiotherapy Peter says 'mummy is going to see captain brain zap' - they understand to a certain degree and we'll always be open with the children.
"Certainly for me, having a brain tumour wasn't something I thought about - you donate money to the cause and then get on with your day.
"My treatment is due to finish December where I will be scanned again to see how the treatment has helped.
"My hope is to get back to 'normal life', at the moment I'm trying not to think beyond January 2023."
GBM Awareness Week takes place in the UK from Monday 18 July.
According to Brain Tumour Research, GBM is the most commonly diagnosed high-grade brain tumour in adults.
It is fast-growing and the average survival time is just 12 to 18 months.
Treatment options are extremely limited and there is no cure.
Mel Tiley, community development manager at Brain Tumour Research, said: "We're sorry to hear about Janet's diagnosis and wish her well in her treatment.
"We're thankful to Janet for sharing her journey of living with a brain tumour to help us raise awareness and the need for more funding into a disease that is indiscriminate and can affect anyone at any age. "
