In 1999, Susan Sheridan’s husband, Pat, went in for surgery to remove a tumor in his neck. After the surgery, the neuro­surgeon gave the Eagle, Idaho, couple great news: The mass was benign—a fact the neurosurgeon confirmed after looking at the pathology report two weeks later.

“Little did we know that the pathologist had been conducting ongoing stains on the tumor and had released a final pathology report 21 days after the surgery,” says Susan, now 48. “It said ‘malignant sarcoma.’” Cancer. But the Sheridans never got this critical update because it was mistakenly filed away at Pat’s doctor’s office without the physician or patient ever seeing it.

Within six months, Pat’s cancer had spread dramatically; he died of it in 2002, at the age of 45, leaving behind two school-age children. Had Pat’s malignancy been aggressively treated after that first surgery, he would likely be alive today. “There was no system in place to make sure a life-or-death document was read,” explains Susan, who discovered the error after requesting Pat’s medical records.

The mistake that cost Pat Sheridan his life took just seconds. Even if most errors don’t have such tragic consequences, the circumstances that prompt them are everywhere—and screwups happen often. In fact, 95% of physicians report having witnessed a serious medical mistake, and 56% say they’ve personally been involved in a serious preventable error, says Sanjaya Kumar, MD, author of Fatal Care: Survive in the U.S. Health System. And these mistakes kill. “To Err is Human: Building a Safer Health System,” the Institute of Medicine’s 1999 seminal report that first brought to light the problem of medical mistakes, noted that up to 98,000 preventable deaths happen each year in hospitals. But deaths in other settings, including doctor’s offices, were about three times that.

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