FDG-PET/CT of sarcoidosis and sarcoid reactions following antineoplastic treatment

Kentaro Inoue,Hideo Shimomura,Ryoi Goto,Hiroshi Fukuda

doi:10.1186/2193-1801-2-113

Abstract

Sarcoidosis or sarcoid reactions, which appear as FDG-avid lesions in oncologic patients, need to be differentiated from disseminated malignancies. We aimed to promote awareness of development of sarcoidosis or sarcoid reactions after antineoplastic therapy to avoid diagnostic errors with FDG-PET/CT findings and assess the utility of FDG-PET/CT for follow-up. We retrospectively reviewed radiological reports of FDG-PET/CT scans performed between January 2009 and December 2011. Among oncologic patients with more than 2 FDG-PET/CT scans, those with nearly symmetrical increases in FDG uptake in the hilar or mediastinal lymph nodes were identified, and those with known sarcoidosis, concurrent diagnoses of sarcoidosis with malignancy, or histopathologically proven malignancies were excluded. Then, only those cases were selected for which sarcoidosis or sarcoid reactions were diagnosed. Four of 376 oncologic cases met the criteria. At 9 months to 6 years after antineoplastic therapy, abnormal FDG uptakes were observed in the hilar, mediastinal, abdominal, pelvic, and inguinal nodes, and/or spleen and lung parenchyma with SUVmax up to 17.7. On the basis of these findings, 1 patient received anticancer chemotherapy because of tumor recurrence suspicion. A gradual decrease in FDG uptake was observed on subsequent PET/CT scans. Sarcoidosis or sarcoid reactions should be considered in differential diagnosis of oncologic patients who have developed FDG-avid lesions any time after antineoplastic therapy. FDG-PET/CT can be used for follow-up in nondiagnostic situations to detect decreases in FDG uptake due to presence of sarcoidal granulomas.

Highlights

Sarcoidosis is a multisystem granulomatous disease of unknown origin that is characterized by the presence of noncaseating granulomas in affected tissues
Of the 376 oncologic patients who underwent more than 2 FDG-Positron emission tomography (PET)/computed tomography (CT) scans during follow-up after antineoplastic therapy, 4 patients were diagnosed with sarcoidosis or sarcoid reactions based on histopathological and clinical data
These unconfirmed cases were not included in this study because the aim of this study was not to indicate the prevalence of sarcoidosis or sarcoid reactions in patients who underwent oncologic FDG-PET/CT scans after antineoplastic treatment

Summary

Introduction

Sarcoidosis is a multisystem granulomatous disease of unknown origin that is characterized by the presence of noncaseating granulomas in affected tissues. Sarcoid reactions (or sarcoid-like reactions), which refer to the development of noncaseating granulomas in patients who do not Positron emission tomography (PET) and PET/computed tomography (CT) with 2-deoxy-2-[F-18]fluoro-Dglucose (FDG) have been widely used in the management of malignancy based on the increased use of glucose by malignant cells. The use of FDG-PET/CT for staging, assessing the response to therapy, and diagnosing the recurrence of malignancy is, hampered by active inflammation and granulation tissues, which are known to accumulate FDG (Shreve et al, 1999). Active sarcoidosis shows high FDG uptake and, can be a pitfall for the diagnosis of malignancies in one respect, but repeated FDG-PET can be used for the assessment of the activity of sarcoidosis and its response to therapy (Teirstein et al, 2007; Braun et al, 2008)

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