Whether lung nodules and hard nodular foci are cancerous or not needs to be determined based on the size and nature of the nodules. Lung nodules and hard nodular foci are mostly caused by early stage tuberculosis. Tuberculosis is prone to proliferation, calcification, nodules, fibrosis, cavity formation and other polymorphic changes in the course of treatment. Hard nodule foci are mostly old lesions and do not need special treatment. If the sclerotic foci are large, especially those larger than 3cm, accompanied by short burr, lobulation, pleural pull sign, pleural depression sign, it means that the sclerotic foci are in an unstable state, and are prone to early lung cancer. Hard nodular foci are also common in inflammatory pseudotumor, tuberculosis ball and other changes, which need to be given chest enhanced CT examination. If necessary, chest lung tissue biopsy should be performed to clarify whether it is early lung cancer. Lung nodules and hard nodule foci that show growth changes with short burrs and lobulation, especially when chest enhanced CT suggests abnormal changes, need to be alerted to early lung cancer.