Breast cancer is a leading cause of death in women under 50 in the UK.
Most cases - 96% - are in women over 40, while 25% are in women over 75.
Men can get breast cancer too, with about 420 new cases every year in the UK.
Natasha Finch was diagnosed with an aggressive breast cancer at just 23 despite having no known risk factors.
She has since become an advocate for breast cancer awareness and wants young women to take symptoms seriously.
"I'm six years on and still here, still winning. Going to the GP was scary, but I'm so glad I went when I did — because if I hadn't, who knows?"
"I just want to advocate for girls."
This study, by a team from Cambridge University and the Institute of Cancer Research, looks at how to predict breast cancer risk in younger women.
They used a risk calculator called Boadicea that combines factors such as family history, lifestyle, reproductive history and genetic information to give a risk score.
If all women under 50 were to have this done, they estimate about a quarter (26.5%) would be categorised as at above-average risk and referred for further assessment.
This would include a third of women under 50 (34.8%) who develop breast cancer within 10 years.
By comparison, the current Nice criteria would result in 1.4% of women under 50 being referred for further assessment, which would include just 4.4% of those women who develop breast cancer.
A main reason for the disparity, the researchers say, is because three-quarters of women (73%) under 50 who develop breast cancer within a decade have no family history of breast cancer - the key criterion in the Nice guidelines.
Lead researcher Dr Juliet Usher-Smith said the NHS should review the criteria in the light of the findings, but acknowledged referring more people would add to workloads and could cause some women unnecessary checks and anxiety.
Dr Sowmiya Moorthie, from the charity Cancer Research UK which funded the work, said: "Any changes must be accessible and equitable, taking into consideration the anxiety that extra referrals might cause for women."
Several breast cancer risk calculators like Boadicea already exist and none are perfect.
Nice said it welcomed the findings and recognised the potential of such multifactorial risk assessment tools but said the current evidence did not warrant a change to its breast cancer guidelines.
The NHS breast cancer screening programme - which advises the NHS for all four nations - is regularly evaluated by the UK National Screening Committee.
The four UK nations run broadly comparable breast screening programmes.
Like most high income countries, women are first invited at 50 and then every three years - though there are some variations.
For example, Sweden, begin screening at the age of 40, while others, including Australia and Canada, offer mammograms every two years rather than every three.
The UK's screening programme, external aims to balance detecting cancer early while minimising the downsides of screening, such as false positives, overdiagnosis and unnecessary treatment, and ensuring the programme remains cost effective.
All women are encouraged to know what looks and feels normal or usual for them and to see a doctor if they notice any changes.
