A ground glass nodule in the lower lobe of the upper lobe of the left lung is not necessarily lung cancer, but if the ground glass nodule grows rapidly over a short period of time, it is likely to be lung cancer. With ground glass nodules in the lower lobe of the upper lobe of the left lung, both benign and malignant disease possibilities are generally considered. Bacterial infections, fungal infections, and allergic diseases occurring in the lungs may form ground-glass nodules, which are usually small and slow-growing, and will shrink or disappear after treatment with anti-inflammatory, anti-fungal, and anti-allergic drugs. On the other hand, ground-glass nodules formed by lung cancer are usually larger and grow rapidly, often in a short period of time, and need to be treated with surgery, medication, radiotherapy and other treatments.