The cavity in the lower lobe of the left lung is not necessarily cancer, but may also be lung abscess, tuberculosis and other diseases. 1. Lung cancer: After the necrosis of cancerous tissues connects with bronchial tubes, the cavity will be thick-walled and eccentric, with uneven inner edge. If the cavity is infected, there will be a liquid plane in the cavity. 2. Lung abscess: the cavity caused by abscess will often have a liquid plane, and there will be a lot of inflammation around the abscess, which often shows a large patchy shadow on imaging. 3. Tuberculosis: Cavitary tuberculosis is a common form of cavities of different sizes, mainly formed by the dissolution of caseous exudative lesions of multiple cavity-like worm-eaten cavities. If any of the above situations occurs, please consult a doctor in time for reasonable and standardized diagnosis and treatment.