Welcome to the first part of an 11-part serial on breast cancer in Marin County. This investigation began more than five years ago, when science journalist Peter Byrne encountered a startling fact: 10 percent of all mammograms produce false positives.
A longtime Bay Area resident, Peter had for years read headlines declaring Marin County the breast-cancer capital of the world. Then he began to dig. He found that high rates of breast cancer screening…