How long it takes for a lung nodule of 5mm to develop into lung cancer is related to the nature of the lung nodule. Most lung nodules are benign and do not easily develop into lung cancer. If there are early signs of lung cancer, the latent period for its development into lung cancer is mostly 5 to 10 years. When a 5mm isolated pulmonary nodule is found in the lung, it is uncertain whether it will develop into lung cancer and how long it will take to develop into lung cancer, and it is necessary to take into account the patient’s own medical history, clinical manifestations, and other relevant examinations such as pathological biopsy to clarify the nature of the pulmonary nodule. 1. If the pathologic biopsy of a lung nodule of 5mm is benign, it is not likely to develop into lung cancer. In this case, it is sufficient for the patient to pay attention to regular review and observe the progress of his/her lesion. 2. If the pathological biopsy of the lung nodule is highly suspicious of precancerous lesions, such as atypical adenomatous hyperplasia or severe squamous epithelial atypia, the time for the lung nodule to develop into lung cancer is usually in the range of 5 to 10 years, but it may be as short as half a year or as long as 12 years due to individual differences. Therefore, when a patient is found to have a 5mm lung nodule, he/she must cooperate with the doctor to perform relevant examinations to clarify the nature of the nodule, and then take active treatment at an early stage or undergo regular review.