Black women are more likely to have breast cancer diagnosed at a later stage than white women, figures suggest.
A quarter of black African women who have breast cancer in England have their disease detected when it is at stage three or stage four.
And 22% of black Caribbean women are diagnosed with their condition at these later stages.
This compared with just 13% of white women who were diagnosed with breast cancer during 2012 and 2013, according to new analysis from Cancer Research UK and Public Health England (PHE).
Differences between stage of diagnosis and ethnicity are yet to be explored but Cancer Research UK said that reasons could include tumour biology, awareness of symptoms and attitudes to cancer and breast screening attendance.
The charity said that reducing late-stage diagnosis is "key" to getting better results for patients.
Dr Jodie Moffat, Cancer Research UK's head of early diagnosis, said: "It's difficult to know exactly what would be behind any differences, but there are likely to be a range of reasons, including possible differences in tumour biology, awareness of symptoms, barriers to seeking help, attitudes to cancer and breast screening attendance."
The charity's head of health information, Dr Julie Sharp, said: "Reducing late-stage diagnosis of cancer is a key part of our work to achieve better results for patients, and we want to be sure that any activity is reaching those most in need.
"Because of the data gaps, we'll need further work to know how accurate the picture is that these results paint.
"But we are clear that finding cancer at an earlier stage can make a real difference as it means treatment is more likely to be successful. If you notice something that isn't normal for you, or you've a symptom that's not gone away or has got worse, getting it checked out promptly could save your life."
This is the first time data on specific ethnicity and stage of diagnosis has been routinely released.
Dr Jem Rashbass, PHE's cancer lead, said: "This analysis will help improve awareness and target treatments. It also shows how vital it is that we collect data is on every person with cancer in England, as findings like these are only possible due to the world-leading cancer data we have in this country.
"It is hugely important to catch all cancers, but particularly breast cancer, early.
"Lumps are not the only sign and women should tell their GP if they notice any changes to their breasts such as nipple discharge or changes to the skin of the breast.
"Breast screening is offered to women aged 50-70 and can help detect cancer earlier and improve survival."