Micro nodular foci in both lungs are mostly caused by benign tumors of the lungs, precancerous lesions, old lung lesions or other lung diseases. 1. Benign tumors of the lungs: when suffering from benign tumors such as lung stenoma, the tumors will be manifested as microscopic nodular foci in both lungs when they are small. 2. Pre-cancerous lesions: when atypical adenomatous hyperplasia and other lesions occur, they will also manifest as nodular foci, and with the change of time, they may be transformed into lung cancer. 3. Old lung lesions: when there is a history of tuberculosis, pneumonia, lung infection, etc., even after cured, the imaging examination will show nodular foci left behind. 4. Other lung diseases, such as pulmonary nodular disease, pneumoconiosis, primary lung cancer, metastatic lung cancer, etc., can also cause such changes. It is recommended to consult a specialized physician at a regular hospital in time.