Flow cytometric quantitation of natural killer cells and T lymphocytes expressing T‐cell receptors alpha/beta and gamma/delta is not helpful in distinguishing benign from malignant body cavity effusions

Background Quantitation of natural killer (NK) cells in benign and malignant effusions has yielded conflicting results in the past. Studies have claimed higher, lower, and essentially equal percentages of NK cells for benign and malignant effusions. In addition, virtually no literature exists on the numbers and distribution of T lymphocytes expressing T‐cell receptor alpha/beta (TCR α/β) and T‐cell receptor gamma/delta (TCR γ/δ) in body effusions. Methods Using multicolor flow cytometry and sequential gating techniques, NK cells and T lymphocytes expressing TCR α/β and TCR γ/δ were identified and quantitated in 30 benign and 30 malignant effusions. Results No significant difference in percentage of NK cells was found between benign and malignant effusions. The absolute number per miroliter of CD16(+)CD56(+) NK cells was higher in malignant than in benign effusions, but only at a borderline level of statistical significance. T cells expressing TCR α/β far outnumbered those expressing TCR γ/δ in all effusions, a distribution similar to that in normal adult peripheral blood and lymphoid tissue. The percentages and absolute numbers of these T‐cell subsets were the same in benign and malignant effusions. Conclusions Enumeration of NK cells and of T lymphocytes expressing TCR α/β or TCR γ/δ in human body effusions is not helpful in attempting to distinguish between benign and malignant effusions. Values for the two T‐lymphocyte subsets in human effusions are, to our knowledge, established for the first time by flow cytometric determination. © 2008 Clinical Cytometry Society