My breast surgeon simply says it's still a mystery as to what causes bc, but we are getting a lot better at treating it! One thing that may be relevant is that breasts lose density as you age. Dense breasts may make it harder to detect anything (self examination or mammograms), particularly if it's minute, pre-cancerous or minute and slow growing. Whereas older women may pick it up more quickly. Current BCNA (2015) stats still state that the mean age for diagnosis is 60 years, that is half the number who get bc are under 60 and half are over.