Proliferative foci are generally referred to as proliferative foci in the lungs, which have a low chance of becoming cancerous, but there is no standardized data on the exact chance. Lung proliferative foci are fibrous foci left behind after treatment or self improvement of infectious diseases in the lungs. Generally, the density of the hyperplasia is slightly higher than that of the surrounding tissues, and the condition is relatively stable and will not change for a long time, so cancer rarely occurs. However, if the patient smokes for a long time or shows serious infection in the lungs when he/she has lung proliferation foci, the chance of cancer will increase. Therefore, patients with lung proliferation foci should stay away from tobacco, actively treat chronic lung diseases (e.g. chronic obstructive pulmonary disease, tuberculosis, tuberculosis, etc.), and go to the hospital for review on a regular basis.