A Japanese hospital is acknowledging that because of a mix-up, last month a woman in her 30s had a breast removed unnecessarily, according to news reports. The woman's tissue samples had been confused with needle biopsies taken the same day from a woman in her 50s.

Told that she had advanced cancer, the younger woman had agreed to have the mastectomy. But when the removed breast was examined, the Chiba Cancer Center, in Chiba, Japan, discovered that she had only early-stage cancer, and had not needed surgery.

The older woman, whose appearance had strongly suggested the presence of cancer, underwent a second biopsy after the mix-up was discovered, and immediately began treatment.

The chain of custody that may have led to the mistake, says the hospital, starts with a doctor who collects the needle biopsy samples, continues with a nurse who labels the container, passes to a nursing assistant who takes the sample to pathology, continues with a clinical technologist who stains the tissue, and ultimately ends with the pathologist who examines it. The mix-up likely occurred somewhere in the process, says the hospital.

The hospital said it wants to "devise countermeasures" to ensure that a similar mistake never happens again. Additionally, it said, it's considering compensating the woman.

Jim Burger