Multiparametric evaluation of flow cytometric synthesis phase fraction determination in dual-labelled breast carcinomas.

Multiparametric, two-color DNA and cell cycle analyses were performed on 112 consecutive mechanically dissociated, ethanol-fixed breast carcinomas using a dual-label method with monoclonal antibodies (CAM 5.2) to cytokeratin (CK) and leukocyte common antigen (LCA) with propidium iodide (PI) staining. There was marked intertumoral variation of CK-positive (range, 3-87%; mean, 40%) and LCA-positive (range, 1-28%; mean, 6.5%) events in DNA histograms. Approximately 70% of DNA aneuploid cells were CK positive. CAM 5.2-stained (avidin-biotin technique) Cytospin preparations correlated with flow cytometric (FCM) detection of CK-positive cells in 15/21 (71%) cases. In each discrepant case, FCM detected greater numbers of CK-positive cells. Cytospin controls of tumor suspensions revealed that cytoplasmic loss was the major cause of decreased CK staining. Synthesis phase fraction (SPF) calculation from CK-gated histograms resulted in kinetic indices (mean ungated, 12.3%, vs. mean CK-gated, 16.8%; P less than .01) with improved statistical correlations with tumor grade and estrogen receptor (ER) status. Differences between ungated vs. CK-gated SPF were greatest in cases having less than 20% CK-positive events (P less than .05). Cases with lower CK staining events generally had higher SPF and were more often high grade (below median CK staining, 61% high grade, vs. above median CK staining, 31% high grade) and ER-negative (below median CK staining, 55% ER negative, vs. above median CK staining, 12% ER negative).(ABSTRACT TRUNCATED AT 250 WORDS)