Occupational lesion in the upper lobe of the left lung with enlarged mediastinal lymph nodes belongs to the diagnosis of the lesion by CT examination, and the diseases that cause the corresponding condition mainly include lung cancer, tuberculosis, lung abscess and so on. 1. Lung cancer: it is a common malignant tumor in the lung, with the progress of the tumor, there may be metastasis of lymph nodes in the mediastinum, and there will be corresponding changes in the examination process. 2. Tuberculosis: after Mycobacterium tuberculosis infection, caseous granulation tissue appears in the upper lobe of the left lung and causes reactive enlargement of lymph nodes in the mediastinum, which will also have relevant manifestations. 3. Lung abscess: it is caused by inflammation, after the infection in the lungs, if the control is not timely, it will cause the abscess in the lungs, because the inflammation will lead to the reactive proliferation of mediastinal lymph nodes, which will lead to the relevant manifestations. If you find occupational lesions in the upper lobe of the left lung and enlarged mediastinal lymph nodes, you need to consult a doctor in time for observation and diagnosis of the lesions, and then carry out standardized treatment under the guidance of the clinician in time after diagnosis to avoid delaying the condition.