Inflammatory pseudotumor of the kidney mimicking malignancy on 18F-FDG PET/CT in a patient with diabetes and hepatocellular carcinoma.

Inflammatory pseudotumor (IPT) is a pseudoneoplastic lesion that most commonly involves lung. We report a case of IPT of kidney associated with hepatocellular carcinoma. CT and PET/CT showed the features of renal cell carcinoma. After radical nephrectomy, histologic examination demonstrated acute pyelonephritis associated with papillary necrosis, and IPT involving renal parenchyma and capsule. Although renal IPT is a very rare tumor, awareness of its existence in the differential diagnosis of a renal mass is critical to avoid misdiagnosis. Clinician should carefully consider differential diagnosis and complications associated with acute or chronic pyelonephritis and papillary necrosis in diabetic patients, particularly.