Until recently, cancer registries have not recorded ethnic data
New research suggests that black women tend to develop breast cancer earlier than their white counterparts, and that the tumours in question may even be biologically different from those of white women.
It is a small study, but if the findings were confirmed, it could have all sorts of implications for both screening and treatment.
It may seem extraordinary, but this is one of the first UK studies to gather a sample of black people with cancer and compare them with white ones.
"It's just not something we've done in this country, and as a result, there is a real dearth of information as to how cancer may affect people of different ethnic groups differently," says Dr Lesley Walker of Cancer Research UK.
"Until we find out, it's very difficult to make sure that people are being offered the best possible service."
Many UK cancer registries have not until very recently started collecting data about the ethnicity of patients.
Studies that have been done on ethnic differences have used what is perhaps not unfairly described as "dirty data".
This has involved going through registers and making assumptions about peoples' ethnic origins on the basis of their postcode or their surname - so if you are black and called Smith, you are most unlikely to be included.
The US in many ways puts the UK to shame when it comes to working out the various risks of both developing disease and dying of it, according to your ethnic group.
While they do not have the highest rate of incidence, African Americans have among the worst survival rates of all US populations for most cancers.
But UK specialists have always treated these figures with care when it comes to making any assumptions about the black British population.
Access to medical treatment in the US is based largely on ability to pay, and black Americans tend to be poorer than white counterparts. This may have a major impact on what stage of the disease they go to the doctor, and the kind of treatment they can expect once they do.
In the UK, everyone is entitled to NHS care.
But whether being poorer to start with affects your chances of developing cancer - and the kind of cancer you develop - remains a moot point.
According to the Joseph Rowntree Trust, if you fall into one of Britain's ethnic minority groups, you are twice as likely to be living in poverty than a white person.
The researchers from the breast cancer study feel confident that socio-economic factors did not get in the way of their findings: by using local statistics on deprivation, they sought to ensure that the white women they followed were "as deprived" as the black ones.
Dr Rebecca Bowen, who led the study, says she strongly suspects that the way in which cancer developed in the black women in her study was to do with biological differences.
But there remains much debate about the role of ethnic biological differences when it comes to ill health.
Professor James Nazroo, a specialist in health inequality at the University of Manchester, says the scientific community have yet to come up with convincing evidence to put biology over socio-economic differences.
"But they may do yet. What's important in the meantime is to make sure everyone receives the same treatment. At the moment everyone has equal access, but treatment may vary once one enters the system."
If biological differences do emerge, we may see a future where drugs need to be tailored to meet the needs of diverse ethnic populations.
"But first we need the information," says Dr Walker.
"In April we will see the start of the Cancer Intelligence Network. The aim is to become the world leader in cancer information - who gets it, how it develops, what works best. At the moment we are a long way from this, but the political will is there now, and I think things are set to change."