S100A9 and cancer: These include: CDH1, MUC1, THBS4, and MSLN for PEs related to cancer; ADA2, CXCL10, and WARS for TB-PEs; CRP, S100A9, and VIM for parapneumonic PEs; and C9, LDHA, HPX, LDHB, and C3 for benign-PEs.