Laser scanning cytometry quantification of estrogen receptors in breast cancer

OBJECTIVE: To describe the laser scanning cytometry (LSC) processing and an alysis developed for the quantitative analysis of estrogen receptor (EX) co ntent in routine paraffin sections of breast carcinomas. STUDY DESIGN: Histologic sections of archival, paraffin-embedded tissues fr om 30 breast carcinomas were labeled for EX with fluoresceinated monoclonal antibody. EX expression was quantified by LSC ann expressed as percent pos itive tumor cells and as histogram distributions of receptor expression per cell. Duplicate sections of the same tumors were stained for EX by a conve ntional immunoperoxidase reaction and percent positive tumor cells counted visually. RESULTS: Percent EX-positive tumor cells by LSC of immunofluorescence-stain ed sections correlated well with conventional (visual) counts of immunopero xidase-stained duplicate sections when the latter were categorized as low,, intermediate or high percent of positive cells. In addition, the marked va riation in relative number and displayed in histogram distribution. CONCLUSION: LSC measurements are fast and objective and can be carried out on sections of paraffin-embedded tissue after routine processing in the pat hology laboratory. In addition, LSC data provide the relative number of ER binding sites per unit of DNA; that may reveal clinically significant skewe d distributions or sub-populations of tumor cells.