Dual-phase FDG-PET imaging shows suspected malignancy that histological examination later confirmed as sclerosing mediastinitis: report of a case.

Sclerosing mediastinitis is a rare, benign disorder that is often indistinguishable from malignancy by conventional imaging techniques. The value of fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in the diagnosis of this disorder has not been elucidated. Recently, a few studies have reported the use of dual-phase FDG-PET imaging in the diagnosis of malignancies. The dual phase contains early- and late- phase images. The maximum standard uptake value (SUVmax) of late phase images of malignant lesions tends to be higher than those of early phase images. The present case showed that early-phase SUVmax was 5.93, and late phase, 8.92. We strongly suspected malignancy from the results of this new imaging technique, though the histological examination of the surgical samples provided the definitive diagnosis of sclerosing mediastinitis, Flieder stage II. This report describes the uncommon use of dual-phase FDG-PET computed tomography in the preliminary diagnosis of sclerosing mediastinitis. It is thought that current imaging studies are insufficient for the diagnosis of sclerosing mediastinitis, and the rarity of this disorder may prevent the development of imaging techniques. Histological confirmation is still essential for the definitive diagnosis of this disorder.