Lakhani (2001) predicts that a woman diagnosed with high-grade, oestrogen receptor-negative breast cancer before the age of 30 years has a 40–45% chance of harbouring a BRCA1 mutation, compared with a 4–5% chance if these parameters are not met (Lakhani, 2001). Many of the features identified in breast cancer in women who are BRCA1 mutation carriers are associated with a poor prognosis. Here, BRCA1 is linked to breast cancer.