What is the probability of a lung tumor not being cancerous?

Depends on size & #.: Lung cancer is the most common visceral cancer in the world today. Because of this, the presence of a mass lesion in the lungs is concerning. Importantly, not all lung tumors are malignant, and that is good news. The most common type of benign tumor is called a pulmonary hamartoma. These benign tumors account for about 10% of small solitary lung lesions identified by imaging studies.