The Eastern Health Authority in St. John's, NL, is sending all tissue samples from breast cancer patients for testing at Mount Sinai Hospital Toronto while a local testing facility is reviewed.

Dr. Bob Williams, vice-president of quality diagnostic and medical services with the health authority, told the St. John's Telegram the decision was made after new information became available concerning a patient in May.

In an initial test to determine if the patient's tumour and tumour cells could be stimulated by the hormones estrogen and progesterone, the result was negative. But subsequent testing of the same tissue with new information from the patient yielded a positive result.

Williams told The Telegram the health authority will suspend all testing of breast cancer patients locally and will send the seven or eight samples taken each week to Mount Sinai for testing. A full quality review is underway of the section of the local lab that had done the tests.

Results going back as far as 1997 are also being sent to Mount Sinai for retesting.

The testing and retesting of some biopsies is not to determine if the cells are cancerous but to determine whether cancerous cells are negative for estrogen and progesterone receptors.

The results of this testing influences the course of treatment for patients.

Williams said surgery is the main treatment for a cancer tumour, but patients testing positive for hormone receptors could be treated with the drug Tamoxifen.

Most of the tests performed in the Newfoundland facility were positive, Williams said.

"We are only re-testing the 27 per cent or so that were negative."

He said about 10 per cent of tests done over the last seven years may show different results.

The reason for the discrepancy in the breast cancer results is unknown, but a new system for detecting hormone receptors in breast tissue was implemented at the lab last year.