Causes of noncancerous, or benign, lung lesions include an infectious fungus, tuberculosis, a lung abscess or pneumonia, according to WebMD. These lesions may also occur due to sarcoidosis, rheumatoid arthritis or Wegener's granulomatosis.
To find out if a lung lesion is benign, a doctor often takes several X-rays over a period of two years, and if there are no changes, the lesion is benign, explains WebMD. A lung lesion grows very slowly, but if it is cancerous, it may double in size every four months. To further ensure the lesion is benign, a doctor may X-ray the lesion for up to five years. Additionally, a benign lesion may have a smoother edge than a cancerous lesion.
If a lesion begins to change shape, size or appearance, the doctor usually orders more tests to rule out cancer or determine a cause, states WebMD. These tests include blood tests, a skin test to check for tuberculosis, a positron emission tomography scan, magnetic resonance imaging or even a biopsy, which means the doctor takes a sample of the lesion and looks at it under a microscope. The doctor may remove the sample through a needle or by performing a bronchoscopy. This is a test that allows the doctor to look at a patient's airway through a thin instrument.