Interstitial pneumonia is not an early symptom of lung cancer; they are two different diseases. Interstitial pneumonia is an inflammatory and fibrotic disease of the interstitium of the lungs. Its known causes include certain dusts (e.g., quartz dust, organic dust), some drugs (e.g., furazolidone, mitomycin), and pigeon droppings, etc.; its typical manifestations are progressive dyspnea (shortness of breath), dry cough, and fever, etc.; its clinical treatment focuses on anti-inflammation and anti-fibrosis in order to slow down the progression of the disease. Lung cancer is a primary malignant tumor originating in the lungs. Its types include squamous carcinoma, adenocarcinoma, large-cell lung cancer, etc. Among its causes, smoking is the most important high-risk factor, in addition to cancer-causing environment, ionizing radiation, etc. Typical clinical manifestations of lung cancer include coughing, hemoptysis, low-grade fever, emaciation, etc. Its treatments include chemotherapy, radiotherapy, and surgical resection.