Pathologists Often Wrong About Estrogen Receptor Status.

SAN ANTONIO -- Misdiagnoses of breast cancer patients' estrogen receptor status have increased sharply since pathology laboratories' near-universal shift from ligand-binding assay to immunohistochemistry, according to Dr. D. Craig Allred.

"I'm convinced that we're misdiagnosing at least 5% of the patients that we see, he said at a breast cancer symposium sponsored by the San Antonio Cancer Institute.

"Extrapolating to the 200,000 newly diagnosed patients per year in this country alone, that's 10,000 patients. That's a lot. And in fact I believe it's more on the order of 10%-15% being misdiagnosed," said Dr. Allred, who has developed a scoring system to improve the diagnostic accuracy of immunohistochemistry (IHC).

Estrogen receptor status is a breast cancer patient's single most powerful predictor of outcome. If she receives a false-negative diagnosis, she'll miss out on the opportunity to receive tamoxifen, a lifesaving drug in women with estrogen- or progesterone-positive tumors. And if she's incorrectly labeled as hormone receptor-positive, she'll be exposed to the risks of tamoxifen without any possibility of benefit.

Still, not everyone places the blame for hormone receptor misdiagnosis squarely on IHC, citing improper tissue handling techniques as a possible cause, he added.

American pathologists embraced IHC for the detection of estrogen and progesterone receptors in breast cancer cells roughly 5 years ago. It's a much less expensive and technically far easier test than the ligand-binding assay it replaced. Moreover, it can be performed on smaller specimens. And unlike the ligand-binding assay IHC doesn't utilize radioactive reagents, so it's safer for lab personnel.

But there are major problems with IHC, chief among them the College of American Pathologists' unwillingness to insist on standardized test methods and ...