Between 30 and 50% of new breast cancer diagnoses are found on mammography screenings and are classified as ductal carcinoma in situ, or DCIS. Most of these "cancers" are not cancer at all. In fact about 97% are benign lesions that can be followed over time quite safely. Most cases of DCIS would be better off under-diagnosed and under-treated.
Unfortunately, most women found to have this condition are frightened into doing surgery, radiation treatment and chemotherapy when they don't need any treatment at all except for watchful waiting.
There are conflicts of interest from Big Pharma, the mammography industry, breast surgeons, and radiologists...they make a lot of money on this group of patients.