Relation between natural killer cells and neoplastic cells in serous fluids

Natural killer (NK) cells are capable of lysing certain tremor cells in vit ro. We investigated whether the percentage of NK cells (NK%) in serous effu sions has any relation with the presence of malignant cells. Fresh effusion s were routinely processed and a portion of them was submitted for lymphocy te immunophenotyping, using a flow cytometer. Fifty-one fluids (15 peritone al, 36 pleural), from 47 patients were analyzed Thirty-two cases were negat ive and 19 were positive for neoplastic cells: there were 13 adenocarcinoma s, 2 malignant mesotheliomas (MM), 3 malignant lymphomas (ML), and 1 rhabdo myosarcoma (R). Negative cases showed an average NK% of 5.09% (1-16%). Effu sions positive for adenocarcinoma had art average NK% of 22.08% (12-33%) (P < 0.001). MM, ML, and R had a low NK%, with an average of 3.01% (0-5%). In vestigation of the NK% could be useful in cytologically doubtful cases and in the differential diagnosis between MM and adenocarcinoma. Diagn, Cytopat hol. 2000;22:347-350. (C) 2000 Wiley-Liss, Inc.