There is no such thing as signal of cancerous lung nodule. You can make preliminary judgment on whether the lung nodule has the tendency of cancerous transformation from clinical symptoms and changes of the nodule. 1. Clinical symptoms: If patients have typical lung cancer symptoms, such as cough, sputum, blood in sputum, fever, emaciation, etc., it may be a signal of lung nodule cancer. 2. Changes of nodules: Patients with lung nodules need to undergo regular review of CT, if the result of review shows that the boundary of the nodules is not clear, there are abundant blood flow signals, or the nodules increase rapidly in a short period of time, it may be a sign of cancerous transformation of lung nodules. If patients have the above symptoms, it is recommended to go to the hospital in time, and if necessary, they need to do pathological examination to clearly diagnose whether the nodules are cancerous or not.