Nodular foci in the upper lobe of the left lung may be associated with diseases such as tuberculosis and lung cancer. Nodular foci in the upper lobe of the left lung suggest tuberculosis changes mostly. Tuberculosis is an infectious disease of the respiratory system caused by infection with Mycobacterium tuberculosis. Typical symptoms are coughing, coughing up sputum, blood in sputum, and systemic symptoms such as low-grade fever, fatigue, and loss of appetite. Nodular foci in the upper lobe of the left lung cannot be excluded as malignant lesions in the lung. Chest CT of lung cancer can show solid nodules, mixed nodules and pure ground glass nodular shadows in the lung. Smoking and air pollution are the main causative factors of lung cancer. Typical symptoms include cough, hemoptysis and chest pain. Nodular foci in the upper lobe of the left lung can also be seen in other diseases, and it is suggested that patients should seek medical treatment in time and check and treat under the guidance of doctors.