A- C. There are bilateral destructive, FDG-avid bony lesions in the occipital bones of the skull vault, with SUVmax up to 2.7.

D- F. A contrast-enhancing, moderately hypermetabolic (SUVmax 4.1), mass is present in the right masticator space, associated with bony destruction of the right mandible. There is invasion of the right masseter, pterygoid muscles, and deep lobe of the right parotid gland. The lesion has central necrosis.

G- I. Images show an FDG-avid soft tissue mass in upper pole of left kidney, with SUVmax 6.7. A small renal cyst is present in the lower pole of the kidney. There is a hypermetabolic mass in the vertebral body of L2, with SUVmax 4.2.

J. MIP cine image shows diffuse bony metastases to the skull vault, multiple vertebrae (T3, T8, L2), and the left ilium. Bilateral inflammatory antro-choanal polyps are noted. There are bilateral gleno-humeral joint changes consistent with known history of rheumatoid arthritis.

Renal cell carcinoma accounts for 85% of renal cancers in adults. As occurred in this patient, renal cell carcinoma frequently metastasizes widely before onset of symptoms or signs. Up to 25% of patients have metastases at presentation, most commonly to lungs and bones, followed by regional lymph nodes, liver, adrenal glands and brain.

PET-CT is a useful method in the detection of primary tumours in patients presenting with carcinoma of unknown primary, as occurred in this case. There are also benefits of PET-CT over conventional methods in the staging of RCC, including ”whole-body” multisystem approach in one study. FDG PET-CT shows promising results and may replace conventional methods for this indication.