Women who have a close history of breast cancer running in their families are more prone to developing the disease at around fifty years of age even if they themselves do not show the genetic mutation linked to breast cancer.
Even if they test negative for the BRCA1 and BRCA2 genetic faults which are predominantly held responsible for causing breast cancer in women, such women still display a higher tendency for developing the disease.
"This is mainly because such women may inherit other gene faults that are still not known to us but may be hugely contributing to the development of the disease", said Professor Gareth Evans, of St Mary's Hospital in Manchester. He further added that, "Although the rise in risk may be small, only about 2-6.4 percent, such women should still be screened regularly for breast cancer starting at an age of preferably thirty- five years".
Breast cancer is the most prevalent form of cancer in women according to the International Agency for Research on Cancer (IARC) in Lyon, France more than a million cases are reported worldwide each year.
Dr. Evans and his team tested the close relatives of 277 women with breast and ovarian cancer or both. In all about 531 relatives, mainly sisters and daughters were tested for the study. It was found that although about half of the women tested negative for BRCA1 and BRCA2 faults still about 28 developed breast cancers and 4 developed ovarian cancers.
Genetic mutation is believed to be the cause for about 5 percent breast cancer cases in developed countries. Dr. Evans added that, "Presently we have knowledge of only two gene faults, but there may be in all about 40 to 50 more genes directly or indirectly responsible for the disease".
The researchers found four different phenocopies of BRCA1 and BRCA2 in women whose results for mutation tests were negative. A phenocopy occurs when a person still develops the condition for which he / she tests negative for genetic mutation.
So it is not just a case of either testing positive or negative for the high risk gene mutation but a horde of factors play a role in deciding the final manifestation of the disease. The occurrence of a phenocopy may be attributed to modifier genes or some other modifications that imitate the changes resulting from a specific gene fault. The findings of the study were reported in the Journal of Medical Genetics.
