CEACAM5 and Pleural effusion: Risk factors suggesting pulmonary metastases in CRC are as follows: patient older than 70, bilateral pulmonary nodules, development of lung nodules after the diagnosis of CRC (metachronous lung nodules), pleural effusion of suspected pleural lesions, primary tumor localized in the middle or lower rectum, advanced-stage CRC presenting vascular invasion, N+ disease, higher preoperative carcinoembryonic antigen (CEA) levels, CRC presenting KRAS mutation and synchronous or metachronous extrapulmonary metastases [33].