TREM1 and Pleural effusion: Analysis of surgical specimens from NSCLC patients demonstrated a high number of TREM-1+ macrophages in tumor tissues and pleural effusions, that was associated with elevated sTREM-1 concentrations and correlated with aggressive tumor behavior, recurrence, and poor patient survival, suggesting that TREM-1+ macrophages are critical players in NSCLC development and progression [194,221,222].