After surgery and chemotherapy, she is cancer-free and eager to begin practicing medicine again. Her story of how she went to the South Pole to be the sole physician for a research station and ended up treating herself unfolds in her new book, Ice Bound: A Doctor’s Incredible Battle for Survival at the South Pole, released earlier this year by Hyperion.

It is a book in which cancer is a main character, but not necessarily the focus. Nielsen spends as much time talking about the incredible place that is the South Pole: it''s extremes and mysterious effects on the human body, and the sense of adventure that moves explorers, scientists and engineers to brave its hostile expanse.

"My attitude about cancer is a little different than most people’s," Nielsen says. "I don’t want to focus on it. I want to forget about it. It''s not your life. It's something that colors your life. It just makes you different. It changes your perspective." She says the illness also brought her closer to her immediate family -- her parents and two brothers.

In the fall of 1998, a 46-year-old Nielsen committed to a year-long stint as physician for a South Pole research station. Her reason for taking a sabbatical from her work as an emergency-room physician was to find some peace and renewal after a difficult divorce and heart-breaking estrangement from her three children.

Before leaving for Antarctica, she endured a battery of physical and psychological testing, including a mammogram.

The mammogram, like the others she had in previous years, was negative. She never gave breast cancer a second thought -- until three months later. She discovered a lump in her breast, while reading and absentmindedly rubbing her chest.

Going back to the US for diagnosis and treatment was no simple matter; although it was spring in the Northern Hemisphere, it was winter at the South Pole -- so cold that jet fuel gels.

Thus began her valiant effort to treat her own cancer while continuing to minister to the stream of fellow "polies" who needed treatment for frostbite, broken fingers, crushed hands, hypothermia, hypoxia (lack of adequate oxygen) and other maladies that come with extreme cold and high altitude. Nielsen performed a biopsy on herself and gave herself chemotherapy using drugs air-dropped to her.

When she became increasingly sick and weak, Nielsen agreed to a heroic Air National Guard crew''s offer to fly in a replacement and bring her back to the US for treatment. At the time, it was the coldest and earliest landing of the season at the South Pole, according to Nielsen. The recent rescue of Dr. Ronald S. Shemenski now holds that record.

Annual mammograms are now shown to reduce the mortality rate of breast cancer by as much as 63%, according to a new report from a long-range study in Sweden. But Nielsen''s case demonstrates the importance of breast self-examination in addition to mammography, she says.

When she first discovered the lump, Nielsen wondered whether her mammogram just a few months earlier had been misread.

"I sent [the mammogram] to friends who were radiologists, and they couldn''t find [any sign of a tumor], even though they knew where it was," Nielsen says. "They didn''t misread it. It just wasn''t there."

While annual mammograms are 85% to 90% effective at detecting breast cancer and the most important tool in reducing breast cancer deaths, they aren''t the only thing you should do, says Debbie Saslow, PhD, director for breast and cervical cancer at the American Cancer Society (ACS).

Saslow says women age 40 and over should have:

• A mammogram every year.
• A clinical breast exam done by a physician, just before the mammogram.
• A breast self-examination once a month, at the same time of the month.

Saslow says clinical breast exams, like self-exams, should take seven to 10 minutes. But not all primary care providers may take that long to do them. If a woman notices that her doctor does a quick 15-second exam, Saslow says, she can ask questions about self-examination, and ask the doctor to show her how to do them. Women who are reluctant to sound confrontational to their doctors, she says, can pose questions such as, "I''ve heard that I should use varying amounts of pressure. Can you show me how to do that?"

"[Dr. Nielsen] found it between mammograms," Saslow says. "That does happen. It''s more likely to have a tumor that just shows up and grows fast when you''re in your 40s."

That''s why the ACS recommends mammograms every year starting at age 40, she says. "Even though women in their 40s are less likely to get breast cancer, when they do, it''s more aggressive," Saslow says.