Did the Vikings bring cancer genes to Scotland?

The largest ever family survey of its kind found a distinct "cluster" of gene mutations.

The researchers speculate that some of these may have originated from Scandinavia - introduced by Viking visitors.

The study, published in the British Journal of Cancer, took 107 families in Scotland and Northern Ireland with a strong history of breast cancer.

Scotland seems to have its own distinctive cluster of cancer mutations, some originating here and others perhaps brought over by invaders Dr Marie Boyd, Beatson Laboratory

Members of these families had suffered almost 400 cases of breast cancer, and 150 cases of ovarian cases.

The best known genes linked to these cancers are the BRCA1 and BRCA2 genes.

Increased risk

Having mutations on these genes is thought to increase your chance of developing cancer.

These "faults" are passed down from generation to generation, meaning that women whose close female relatives developed breast cancer are more likely to get it themselves.

However, almost half the mutations detected by the team involved just 10 types of genetic damage, five on each BRCA gene.

This, say geneticists, points to the close-knit ancestry of Scottish and Northern Irish people.

A couple were particularly common, accounting for a quarter of all the detected mutations.

Viking raiders

The first is thought to have originated in west-central Scotland or Ireland, the other was common in Aberdeen or Dundee families.

It is the latter which may have been introduced from Scandinavia.

Dr Marie Boyd, from the Beatson Laboratories in Glasgow, said: "Scotland seems to have its own distinctive cluster of cancer mutations, some originating here and others perhaps brought over by invaders.

"Knowing which genetic faults we can expect to find will make genetic testing and counselling much easier, helping genetics clinics improve the services they provide for Scottish women."

While faults on the BRCA genes may help doctors determine if an individual woman is at increased risk of breast cancer, the overall percentage of breast cancers attributable to BRCA mutations is small.

The bulk of breast cancers are caused by something else - environmental or hormonal factors may be important in many cases.

Sir Paul Nurse, the chief executive of Cancer Research UK, which funded the study, said: "This gives a fascinating insight into the ancestry of the Scottish and Northern Irish populations, but, importantly, it also provides the basis for a more efficient testing procedure for breast cancer genes.