What is the mass found on a lung during a ct-scan be?

Infection, Cancer, +: Infection, hemorrhage, tumors (benign and malignant (cancerous)) fluid and even fibrosis can have a similar appearance. If it is mostly calcified, it is likely benign, old infection called a granuloma. Comparison to older scans can help determine if it has grown. The concern is whether or not it is cancer. Recommend seeing a primary care provider, perhaps a pulmonologist consult and pet/ct.