Chen Z, et al. - Researchers here focussed on studying tumor markers (TM) in pleural effusion (PE). They analyzed TM in PE and serum to ascertain if intrathoracic and extrathoracic tissues express TM. They further tested the associations between serum TM and tumor size, TNM stage of lung adenocarcinoma. Associations between serum TM and tumor size, TNM stage of lung adenocarcinoma were supported by the expression characteristics of TM in PE and serum. They observed a positive correlation of serum CEA, serum CA125, and serum CA15-3 with tumor size, T stage, N stage, M stage of lung adenocarcinoma. They also observed a positive correlation of serum CA19-9 with N stage, and M stage of lung adenocarcinoma; however, no correlation of serum CA19-9 with tumor size and T stage was evident. No correlation of serum AFP with tumor size, T stage, N stage, and M stage of lung adenocarcinoma was observed.