Some diseases of the lung are easily confused with lung cancer, and attention should be paid to the differential diagnosis. 1. Tuberculosis: (1) Tuberculosis spheres should be differentiated from peripheral type lung cancer. Tuberculosis spheres are mostly seen in young patients, and the lesions are mostly found in the areas where tuberculosis is well developed, such as the posterior segment of the upper lobe of the lung and the dorsal segment of the lower lobe. The lesions are usually asymptomatic, have clear borders, are dense, and may have an envelope. Sometimes it contains calcified spots surrounded by fibrous nodular lesions that remain unchanged for years. (2) Pulmonary hilar lymph node tuberculosis Easily confused with central lung cancer, mostly seen in children and young adults, with fever, night sweats and other symptoms of tuberculosis toxicity. Tuberculin test is often positive, and anti-tuberculosis treatment is effective. Lung cancer is mostly seen in adults above middle age, with rapid lesion development and more obvious respiratory symptoms. Sputum exfoliative cytology and fibrinoscopy are useful for differential diagnosis. (3) Cornular tuberculosis should be distinguished from diffuse bronchoalveolar carcinoma. Usually, patients with cornular pulmonary tuberculosis are younger, with fever, night sweats and other symptoms of systemic toxicity, and respiratory symptoms are not obvious. x-ray shows small, evenly distributed, dense corn-like nodular lesions, and fibrinoscopic lung biopsy can often help to make a clear diagnosis. 2.Pneumonia: About 1/4 of early lung cancer is manifested in the form of pneumonia, which needs to be differentiated from general pneumonia. In case of slow onset, no toxic symptoms, slow absorption after antibiotic treatment, or recurrent pneumonia in the same area, the possibility of lung cancer should be considered, especially for segmental or lobar lesions with volume reduction. Chronic inflammatory mechanization of the lung, forming a mass-like inflammatory pseudotumor, can also be easily confused with lung cancer. However, inflammatory pseudotumors often have an irregular shape, uneven margins, a denser core, and are easily accompanied by pleural thickening, and the lesions do not change significantly in the long term. 3.Lung abscess: cancerous cavity secondary to infection should be distinguished from primary lung abscess. The former has lung cancer symptoms first, such as irritating cough and recurrent sputum and blood, followed by infection and increased cough. Primary lung abscess has a rapid onset and serious toxic symptoms, mostly including chills, high fever, cough and coughing up large amounts of purulent sputum. X-ray of the lungs shows large lamellar inflammatory shadows, and deeper fluid levels are common in the cavities. Routine blood tests may reveal an increase in white blood cells and neutrophils. 4.Tuberculous pleurisy: The pleural fluid of tuberculous pleurisy is mostly transparent, straw yellow and sometimes bloody. Cancerous effusion is mostly bloody. When the tumor obstructs the lymphatic vessels, it can cause leaky pleural fluid. Routine pleural fluid, tuberculosis bacilli and pathological examination can help in diagnosis. 5.Nodular disease: Typical nodular disease presents with bilateral symmetrical lymph node enlargement in the hilum and mediastinum, which may be accompanied by reticular, nodular or lamellar shadows in the lung. Tissue biopsy pathological diagnosis can help in the diagnosis. 6. Mediastinal lymphoma: It is quite similar to central lung cancer, often bilateral, and may have systemic symptoms such as fever, but bronchial irritation symptoms are not obvious, and sputum exfoliation cell examination is negative. Mediastinal lymph node biopsy is helpful for diagnosis. 7. Benign tumors of the lung: Many benign tumors are similar to malignant tumors in terms of imaging. In particular, bronchial adenomas and malignant tumors are more difficult to differentiate. If necessary, biopsy should be performed.