He was my patient. A serious and educated 55- year-old man with a diagnosis of metastatic colon cancer waiting to start chemotherapy. I started my usual physical examination, normal conjuntival coloration, normal heart sounds, but something keeps my attention: no ventilation in the left basal lung. No signs of pleural effusion or atelectasia. No dyspnea or thoracic pain. I asked for a thoracic X-ray but nothing attracts my attention.