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Results of Many Breast Biopsies May Be in Error, Authors Find

Pathologists agree with expert panel only 75% of the time

Women who have breast biopsies to diagnose cancer might want to think twice about the results of the procedures, according to a new study led by University of Washington researchers.

Pathologists across the U.S. who were being tested for their accuracy got the same results as a panel of experts only about 75% of the time, a variability in opinion that could have a direct effect on the way women are treated –– or not –– for potential breast cancer.

The findings were published March 24 in JAMA.

About 1.6 million women in the U.S. have breast biopsies each year, and about 80% of these biopsies come back normal. But the remaining results may not be as valid as expected, said study leader Dr. Joann G. Elmore.

Overall, the pathologists were very good at identifying invasive breast cancer (the most serious diagnosis), agreeing with the expert panel in about 96% of cases. But when it came to diagnosing ductal carcinoma in situ (DCIS), a noninvasive condition, they were in line with the experts about 87% of the time. And with atypical ductal hyperplasia, in which abnormal cells are detected, the pathologists matched the experts 48% of the time.

The new study provides the first updated analysis of pathologist disagreement since the 1990s.

Elmore and her colleagues compared the findings of 115 pathologists in eight states –– Alaska, Maine, Minnesota, New Hampshire, New Mexico, Oregon, Vermont, and Washington –– with the results of an expert panel between November 2011 and May 2014.

The participating pathologists were randomly assigned to review one of four test sets of 60 breast biopsy slides, offering a diagnosis for each case. The slides were weighted to include more-than-expected cases of atypia and DCIS, as well as cases from women aged 40 to 49 years and cases from women with dense breast tissue, because age and breast density are important risk factors for both benign breast disease and cancer, the study noted.

Compared with the experts, the pathologists under-interpreted or missed about 4% of invasive carcinomas, about 13% of DCIS cases, and about 35% of atypia cases, the researchers found. Pathologists over-identified atypia in about 17% of cases, DCIS in 3% of cases, and benign breast disease without atypia in 13% of cases.

The level of disagreement was higher among pathologists who interpret fewer cases each week and those who worked in smaller practices or nonacademic settings.

Of the DCIS cases identified by the pathologists, about 18% were not DCIS, which is typically treated in the same way as invasive carcinoma. This means that, based on the diagnoses, many women would be advised to undergo lumpectomy, mastectomy, and other treatments that weren’t actually warranted, said Dr. H. Gilbert Welch, a professor of medicine at Dartmouth University, who was not involved in the study.

The new study suggests that women given the option of “watchful waiting” or having biopsies might want to delay, especially for certain diagnoses, Elmore said. It’s reasonable to seek a second opinion about whether a biopsy is necessary –– or about the results of completed biopsies –– before moving forward.

Source: Medical Xpress; March 24, 2015.

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