Some lung lesions are caused by bacterial infections such as tuberculosis, histoplasmosis, gryptococcosis, aspergillosis or coccidioidomycosis, according to Healthline. Lung lesions are also caused by benign and malignant cancers, which account for approximately half of all lung lesion diagnoses. The most common cause of malignant lung lesions is lung cancer, while up to 30 percent of cancerous lung lesions result from cancer that spreads from another area of the body.
If lung cancer is suspected, the doctor may order specialized tests to search for cancer cells and rule out other possibilities, such as bacterial infections, explains Mayo Clinic. More common tests, such as X-rays and computed tomography, reveal abnormal lung masses of all sizes. In a procedure called sputum cytology, the presence of lung cells is detected by analyzing sputum in people who are producing sputum when coughing.
A biopsy, in which a sample of the abnormal cells is collected and examined, is also an option, notes Healthline. A doctor may recommend a biopsy if a lesion exceeds 3 centimeters across, the appearance of size of the lesion changes, additional symptoms of lung cancer are present or the patient smokes. Biopsy types include a lung needle biopsy, where a needle is inserted via the chest wall. A scope passes down the throat and into the lungs in a bronchoscopy. In a mediastinoscopy, the area between the lungs is lit with a medical instrument.