What causes early onset breast cancer in a population-based sample of Australian women with a strong family history?

MC Southey, AA Tesoriero, SG Royce, L Smith, P MacAulay, J Cui, MA Jenkins, GS Dite, RL Milne, G Chenevix-Trench, A Spurdle, GG Giles, MRE McCredie, DJ Venter, JL Hopper