ABSTRACT
BACKGROUND: Fixation of cells is a critical procedure that can determine the success of immunocytochemical staining (ICC) of cytospin slides. In this study, we evaluated the efficacy of a number of fixatives to determine the ideal fixative for ICC of cytospin slides. METHODS: Sixteen patients with metastatic neoplasm in the body cavity were enrolled. Cytospin slides were prepared from each patient using 5 different fixatives (cold acetone, 95% ethanol, 1:1 methanol:ethanol, 3.7% formalin, and 3:1 methanol:acetone), and the suitability of each for use with Wright's stain was compared. For 4 of the samples, appropriate ICCs were performed using all 5 fixatives and the results were compared, while for 11 samples, only the first 3 fixatives were used for ICC. RESULTS: Using Wright stain, cold acetone, 95% ethanol, and 1:1 methanol:ethanol fixatives all showed similar efficacy when compared to the conventional methanol fixation method. However, the stain quality using 3.7% formalin or 3:1 methanol:acetone fixatives was poor due to deterioration of cell adhesion and distortion of cell morphology. Using ICC, cold acetone fixative showed stronger and more tumor-specific stainability than the 95% ethanol (decreased stainability in 6 stained slides, false positive staining of histiocytes/neutrophils in 4 stained slides, no staining of CD3 and terminal deoxynucleotidyl transferase [TdT]) and 1:1 methanol:ethanol fixatives (decreased stainability in 3 stained slides, false positive staining of histiocytes/neutrophils in 2 stained slides, no staining of CD3 and TdT). CONCLUSIONS: Cold acetone fixative was the most efficacious among the 5 fixatives tested in this study; therefore, it is the most appropriate fixative in the preparation of cytospin slides for ICC.