The "internal wiring" of breast cancer can predict which women are more likely to survive or relapse, say researchers.
The study shows that breast cancer is 11 separate diseases that each has a different risk of coming back.
The hope is that the findings, in the journal Nature, could identify people needing closer monitoring and reassure others at low risk of recurrence.
Cancer Research UK said that the work was "incredibly encouraging" but was not yet ready for widespread use.
The scientists, at the University of Cambridge and Stanford University, looked in incredible detail at nearly 2,000 women's breast cancers.
They went far beyond considering all breast cancers as a single disease and beyond modern medicine's way of classifying the tumours.
Doctors currently classify breast cancers based on whether they respond to the hormone oestrogen or targeted therapies like Herceptin.
The research team analysed the genetic mutations inside the tumour to create a new way of classifying them.
Breast cancer is not one disease but 11, say researchers.
Previous work by the group has shown breast cancer is 11 separate diseases, each with a different cause and needing different treatment.
By following women for 20 years, they are now able to show which types of breast cancer are more likely to come back.
Prof Carlos Caldas tod the BBC: "This is really biology-driven, it's the molecular wiring of your tumour.
"Once and for all we need to stop talking about breast cancer as one disease, it's a constellation of 11 diseases.
"This is a very significant step to more precision-type medicine."
Change treatment
It showed that triple negative breast cancers - one of the hardest types to treat - were not all one class of cancer, but two.
Prof Caldas said: "One where if women have not relapsed by five years they are probably cured, but a second subgroup are still at significant risk of later relapse."
The research could help inform women of their future risk, but may also change the way their cancers are treated.
There were four subgroups of breast cancer that were both driven by oestrogen and had a "markedly increased" risk of recurrence.
These women may benefit from a longer course of hormone therapy drugs like tamoxifen.
Cancer Research UK estimated that 12,300 women a year have such types of cancer in the UK.
Analysis
By James Gallagher, health and science correspondent, BBC News
Cancers tend to be named after the place you find them: breast, colon, prostate, lung - the list goes on.
But it has long been known that this is not good enough.
This study shows the future of personalised medicine and tailoring treatment to the specific causes of someone's cancer.
Studies are already under way looking at which treatments may work best for different subtypes of breast cancer.
And other research groups are trying to get a similar insight into other forms of cancer too.
However, the way the scientists analysed and sorted the cancers is still too complicated to be introduced to the NHS.
It will need refining into a form that could be used as a routine way of analysing a woman's cancer.
Much larger studies involving up to 12,000 women are also planned, so that researchers can be certain of their results.
Prof Caldas said: "I would not recommend it clinically yet, but we really are committed to making this available.
"We are totally committed to having an NHS test, we haven't patented any of this."
Prof Karen Vousden, Cancer Research UK's chief scientist, said: "We're still a way off being able to offer this type of detailed molecular testing to all women and we need more research to understand how we can tailor treatments to a patient's individual tumour biology.
"But this is incredibly encouraging progress."
Latest Stories
-
Cash Waterfall Mechanism report shows significant non-compliance with formula for revenue allocation – Report
4 mins -
Prison officer injured in clash with soldiers in Bawku
7 mins -
SSNIT reserves projected to hit zero in 12 years – ILO
12 mins -
Prestigious Nigerian school closed over bullying reports
16 mins -
Funny Face failed to perform at my show after taking money – Parrot Mouth
22 mins -
CAFCC: Sports Minister to offer Dreams FC a ‘surprise’ package before Zamalek clash
34 mins -
CAF awards 3-0 win to RS Berkane, after Algerian customs confiscated their kits
49 mins -
AgriTech challenge pro holds first pitch
54 mins -
UNIDO commits to improving local rice standards
55 mins -
Suleja prison: 108 inmates on the run in Nigeria
57 mins -
We object to government’s plans to make BEST sole off-taker of Sentuo Oil Refinery – CBOD
1 hour -
Burkina Faso army massacred 223 villagers in revenge attack – HRW
1 hour -
Lebanese Community awards ¢100K in scholarships to 21 students at UniMAC
1 hour -
Germany detains alleged Nigerian mafia members
1 hour -
Manhyia Palace hosts royals, dignitaries from Ghana and beyond at special Awukudee
1 hour