For the six-year study, 196 women with a BRCA1 or BRCA2 mutation, aged 21-68 years, underwent hospital check-ups every six months.
They were examined by a specialist, underwent mammography and, when possible, MRI.
During the study, 81 women (41 per cent) had at least one positive MRI or mammogram. But just 17 women had breast cancer confirmed.
The probability of women having a false-positive result was 83 per cent.
Consultant genetic oncologist at University College London Dr James Mackay said: 'This shows false positives are a problem. It highlights how important it is to explain this possibility to patients undergoing imaging.'
In 2006, NICE recommended annual MRI screening for women with BRCA1, BRCA2 or TP53 mutations or a high family risk of breast cancer.
Comment below and tell us what you think