Before a cancer diagnosis, a woman may have a suspicious mammogram or a man's blood test may reveal a high PSA level. But only with a biopsy, or tissue sample, can a pathologist see the disease.
It is then up to your doctor to break the news.
"Nobody wants to say it," said Teresa Gilewski, a medical breast oncologist at Memorial Sloan-Kettering Cancer Center in New York. "Nobody wants to hear it. But there's hope there. You can do something about it."
At Memorial Sloan-Kettering, one of the premier cancer centers in the country, doctors have identified what patients can do to help themselves.
First, they say, bring a friend or family member to hear the diagnosis. Less emotionally involved, they can take detailed notes on what the doctor says.
Request copies of all case documents -- including test results, X-rays, pathology reports and case summaries.
"Even if you don't understand what they mean at that moment," Gilewski said, "the odds are that as time goes on, you're going to be researching a lot of details about your cancer."
In most cases, doctors say patients should not rush into treatment.
"You certainly have weeks or sometimes, with prostate cancer or other slow-growing cancers, you may have months to make a decision," said Peter Scardino, chairman of the department of urology at Memorial Sloan-Kettering.
Doctors say patients should use that time to verify the diagnosis, using another pathologist at another hospital.
In one study where thousands of biopsy slides from across the country were sent to a major medical center for review, one out of every 71 cases was misdiagnosed.
Once cancer is confirmed, doctors say seek different specialists to discuss treatment options.
If you were originally seen by a surgeon, consult a radiologist or a medical oncologist to get different perspectives.
There are a variety of Web sites, including the National Cancer Institute and the American Cancer Society that can help guide patients. The Johns Hopkins Web site allows patients to ask a pathologist a specific question about a breast cancer case.
Ultimately, doctors say, the more involved patients become, the better the care they receive.
"You can stimulate your doctor to be on his or her toes," Scardino said, "and do the best job when you ask the right questions and ask for the right kind of information."
ABC News' John McKenzie filed this report for "World News Tonight."