Discrepancy in ER levels of breast carcinoma in biopsy vs mastectomy specimens.

The presence of estrogen receptors (ER) in breast tumors has been used by many as the major indicator for hormonal treatment of breast cancer. However, multiple factors have been shown to be involved in determining the hormone dependence of breast cancer. This paper reports another factor that influences the accuracy of ER determination. From January 1977 through December 1983 fifty-eight (58) of these patients had ER determination of both biopsy and mastectomy specimens. Of the 31 patients that remained ER positive in mastectomy specimen, 13 had significantly lower ER levels (by at least 50%) from the mastectomy specimens. These findings indicate that ER status is greatly influenced by the source of the specimen.