It is not yet clear how -- or if -- this will affect American women but a piece of the breast cancer puzzle has been located for Icelandic women. Scientists reported this week that women with a bad gene that raises their risk of breast cancer were almost certain to develop the disease if they also had a mutation of second gene. This gene -- BARD1 -- seems to add a large risk for these women.

Two genes -- BRCA1 and BRCA2 -- were discovered 10 years ago and account for 10-15 percent of total breast cancer cases. Scientists have been searching for other genes that act alone or with these two genes to raise the risk for breast cancer. BARD1 appears to be one of the genes they were looking for.  Women with a BARD1 mutation and also a BRCA2 mutation -- the  most common in Iceland -- have a 50 percent increase in risk. In the United States, BRCA1 is most common so the puzzle is not quite the same. So for the 213,000 American cases of breast cancer that will emerge this year -- making it the most common major cancer in women and the second leading cause of deaths in women -- it is uncertain if BARD1 will be significant. But the discovery of this gene will help unravel the mystery of breast cancer -- and that is a step in the right direction for sure.