New York Times investigative reporter Stephanie Saul has written a disturbing article about the high number of breast biopsies — by some estimates, 17 percent — that are mistakenly diagnosed as ductal carcinoma in situ (D.C.I.S.), the earliest stage of breast cancer, when they are actually benign tumors.

As a result, thousands of women are undergoing disfiguring surgery and radiation treatment and taking potent drugs, such as tamoxifen, unnecessarily.

Writes Saul:

[D]iagnosing the earliest stage of breast cancer can be surprisingly difficult, prone to both outright error and case-by-case disagreement over whether a cluster of cells is benign or malignant, according to an examination of breast cancer cases by The New York Times.

Advances in mammography and other imaging technology over the past 30 years have meant that pathologists must render opinions on ever smaller breast lesions, some the size of a few grains of salt. Discerning the difference between some benign lesions and early stage breast cancer is a particularly challenging area of pathology, according to medical records and interviews with doctors and patients.

Diagnosing D.C.I.S. “is a 30-year history of confusion, differences of opinion and under- and overtreatment,” said Dr. Shahla Masood, the head of pathology at the University of Florida College of Medicine in Jacksonville. “There are studies that show that diagnosing these borderline breast lesions occasionally comes down to the flip of a coin.”

Pathologists frequently disagree on what exactly constitutes D.C.I.S., reports Saul, and [v]ariations in diagnosis may depend on where a woman is treated.”

This issue of misdiagnosis, she adds, takes on

added significance when combined with criticism that it is both overdiagnosed and overtreated in the United States — concerns that helped fuel the recent controversy over the routine use of mammograms for women in their 40s.

The United States Preventive Services Task Force, an independent panel that issues guidelines on cancer screening, found last November that the downside of routine annual mammograms for younger women might offset the benefits of early detection. The panel specifically referred to overdiagnosis of D.C.I.S., as well as benign but atypical breast lesions that left undetected would never cause problems.

What are the 50,000 American women who are told each year that they have D.C.I.S. to do, given all this confusion? First and foremost, don’t feel you have to rush into a treatment decision, suggest the experts quoted in the Times article:

Fear compounds the confusion, and even though D.C.I.S. is 90 percent curable, there is growing concern that women and their doctors opt for more aggressive surgery, radiation and drug therapy than is needed.

A mastectomy is sometimes offered as an option for D.C.I.S., although experts say it is usually not advisable unless the D.C.I.S. is large or appears in several sites in the breast.

Yet more women who are faced with the diagnosis of D.C.I.S. become so fearful that they elect to have both breasts removed, often against their doctor’s recommendations.

“The patient gets paralyzed with a fear of cancer,” Dr. Masood said. “They want the breast off.”

Among women who had surgery for D.C.I.S., the rate of double mastectomy rose to 5 percent in 2005, from 2 percent in 1998, according to a study last year.

Dr. Ira J. Bleiweiss, chief of surgical pathology at Mount Sinai Medical Center in New York, said that ideally, all breast cancer diagnoses would be referred for a second opinion [and by a pathologist with special certification in reading breast tissue]. He warns patients and their doctors: “Don’t rush to the operating room.”

As one woman who was misdiagnosed with D.C.I.S. — and, as a result, had a quarter of her breast unnecessarily removed — told Saul:

“I think you could handle the disfigurement a little bit more if there’s a real purpose for it. The tough part is to find out later that I didn’t need it, and I never did.”