Evaluation of in vivo breast fine needle aspirates by flow cytometry: an efficacy study.

Abstract

Malignancy of the breast is frequently diagnosed through fine needle aspiration. In the hands of a skilled aspirator and cytopathologist, this can be a highly accurate procedure. This study was undertaken to evaluate whether sufficient residual cells in the bore of the needle could be harvested and analyzed efficiently by flow cytometry analysis. The goal was then to determine the value of routine flow cytometry as an adjunctive technology in the interpretation of breast fine needle aspirations. Cells were rinsed from the needles of 83 consecutive diagnostic fine needle aspirates after preliminary inspection had confirmed adequate material was obtained for cytopathology. Cells were washed, and nuclei prepared by detergent treatment. After ribonuclease treatment, DNA was stained with the fluorescent marker propidium iodide. DNA content per cell was determined by flow cytometry by measurement of right-angle fluorescence. Less than 4% of the samples were rejected for inadequate cell numbers. Flow cytometry criteria for evidence of malignancy included the presence of a DNA aneuploid population or an elevated rate of proliferation (13% or higher) of a diploid population. Accuracy of flow cytometry was based on cytopathologic interpretation in all cases except two which were based on results of excisional biopsy. The sensitivity of the flow cytometry analysis was 76%; the specificity was 100%, with results from flow cytometry pivotal in the correct diagnoses for two patients whose cytopathologic results were equivocal. Analysis of histograms indicated acceptable coefficients of variation for all populations. Gating analysis indicated the suitability of the material for this type of study, with an average of 85% of the events selected, or "gated in." Low recoveries were associated with the presence of necrotic debris in the sample. Flow cytometry can be a valuable adjunctive technology, capable of providing the cytopathologist with additional information regarding the character of cells analyzed.