Public Release: 

Errors in cancer diagnosis put patients in harm's way


Procedures used to obtain and examine tissue for cancer diagnosis are prone to error that frequently results in harm, according to a new study published in the November 15, 2005 issue of CANCER (, a peer-reviewed journal of the American Cancer Society. Agency for Healthcare Research and Quality-funded researchers say that a governmentally mandated error detection method that involves the review of patient specimens, when patients have two or more specimens from the same body site, found up to 12 percent of reviewed specimen pairs had an erroneous diagnosis. However, pathologists failed to agree on the cause of most of these errors.

The frequency and cause of errors in cancer diagnosis has not been well studied partly because of the lack of national standards to detect errors. To characterize the frequency, cause, and impact of errors in cancer diagnosis, Stephen S. Raab, M.D. of the University of Pittsburgh School of Medicine and colleagues reviewed tissue specimens, pathologists' findings, and medical records from four institutions that diagnose precancerous and cancerous lesions. Patients often have multiple tests in order to diagnose cancer, and the researchers reviewed patient material when the diagnoses differed on multiple tests from the same patient.

They found that errors were relatively frequent and institution-dependent. Up to 9 percent of gynecologic specimen pairs (Pap test and cervical biopsy) contained an error and up to 12 percent of non-gynecologic specimen pairs contained an error. Differences in institutional error rates are most likely related to bias in error reporting, although underlying quality improvement methods may have resulted in lower error frequencies at some institutions.

The majority of errors were a result of sub-optimal specimen collection, and the proportion of errors caused by pathologist misinterpretation ranged from 5 percent to 50 percent. When pathologists reviewed specimens from other institutions they frequently disagreed with the assignment of error cause.

Review of medical records showed that gynecologic errors resulted in harm in 45 percent of cases and non-gynecologic errors resulted in harm in 39 percent of cases. Harm most likely consisted in delays in diagnosis and additional testing that drove up healthcare costs. It is very rare that unneeded procedures are performed for the false positive diagnosis of cancer. Pathologists also disagreed on the severity of harm that was caused by an error in cancer diagnosis.

The researchers say that their study demonstrates not only a relatively high frequency of error using this detection method, but that variability in practice impairs the ability to understand error cause. To that end, "the standardization and uniform reporting of errors in cancer diagnosis is a first step in improving safety," conclude the authors.


Article: "Clinical Impact and Frequency of Anatomic Pathology Errors in Cancer Diagnoses," Stephen S. Raab, Dana Marie Grzybicki, Janine E. Janosky, Richard J. Zarbo, Frederick A. Meier, Chris Jensen, and Stanley J. Geyer, CANCER; Published Online: Monday, October 10, 2005 (DOI: 10.1002/cncr.21431); Print Issue Date: November 15, 2005.

Contact: Clare Collins, University of Pittsburgh, 412-624-2607, email:

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