A 100% diagnosis rate via mammogram and/or pathology is an oxymoron. The NHS Blog Doctor sheds more light:

If you work in hospital medicine as either a Consultant Radiologist or a Consultant Hispto-pathologist you make a hundred decisions a day. And each and every decision is recorded and stored away for ever. Five hundred decisions a week or more. Twenty five thousand decisions a year. That is probably a million decisions in a working life time.

Make a one in a million mistake and some one may die. Make a one in thousand mistake and, over your career, a thousand people may die. Ask yourself, could you live to that standard? Could you honestly say that for every thousand decisions you make at work, not even one is wrong? And if you did have to live to that standard, how much pressure would it put you under.

Radiologist and histo-pathologists look at X-Rays and mammograms and slides of tissue biopsies and they make a few mistakes. Less than one in a thousand, less even than one in ten thousand. But they do make mistakes. Even doctors are not perfect.