In all studies conducted up to now on tumour series, TREM-1 proved to be associated to aggressive courses or prognosis, perhaps through its expression on dendritic cells [17]: its negative prognostic role was observed in non-small cell lung cancer, by measuring the molecule in pleural effusions [15]; the expression levels of TREM-1 gene are more higher in primary and metastatic colon carcinomas than in colonic normal mucosa [18]; aggressiveness of hepatocellular carcinoma seems to be also affected by TREM-1 immunohistochemical expression on stellate cells [19,20]. This evidence concerns the gene TREM1 and Pleural effusion.