A-C. In the left lower lobe, there is a large mass with central low density and cavitation containing an air-fluid level suggestive of necrosis. The mass is hypermetabolic in the non-necrotic portion with SUV_max of 14.9, and is consistent with the patient's known squamous cell carcinoma. Anteriorly, the tumour and associated conglomerate lymphadenopathy extends to the left hilar region, encasing the left upper lobe, lingular and lower lobe bronchi. Medially, the mass abuts the thoracic aorta. Posteriorly, the mass extends to the left posterior pleural surface. There are also post-obstructive changes in the adjacent lung.

D. Superior to the mass, there is a small cavitatory lesion (arrow) in the apico-posterior segment of the left lower lobe. The metabolic activity of this lesion (not shown) was SUV_max 2.2.

E. Inferior to the mass in the left lower lobe, there are small centrilobular nodules and tree-in-bud opacities, suggestive of an atypical infection. These nodules were eumetabolic (not shown).

For lung cancer staging, integrated PET-CT outperforms PET or CT alone. It provides a detailed view of the anatomy and improves functional correlation. False-positive results however, are sufficiently frequent to require sampling in some positive cases. Concurrent infectious disease, as occurred in this case, should be considered in endemic areas and in patients who are immunosuppressed due to treatment.

Tuberculosis is a common radiologic mimic of cancer, with FDG uptake patterns indistinguishable from cancer. Fusion with CT improves specificity slightly, using morphologic criteria. A described method that may help differentiate tuberculosis and cancer is the combined use of F-18 FDG and C-11 acetate, as the latter accumulates in tumours but not in inflammatory lesions. In the future, radiolabelling of antituberculous drugs, such as isoniazid and rifampicin, may improve specificity.