Sarcoidosis Mimicking Malignancy or Infection in the Chest: Importance of Collaborative interpretation of CT and F18 FDG PET/CT

Objectives: Sarcoidosis is a multi-systemic disease characterized by formation of non-caseating granulomas in various organ systems. Classic imaging findings and patterns of sarcoidosis involving the chest are quite well known. However, less common/atypical findings and marked FDG avidity may lead to false-positive results of malignancy or infection. In addition, sarcoidosis can occur in oncological patients who underwent chemotherapy (sarcoid reaction) for other disease entities such as lymphoma.

Methods: Variable imaging findings of intrathoracic sarcoidosis are reviewed in conjunction with CT and FDG PET/CT. Majority of cases in this presentation confirmed through biopsy or continued follow up. 1. Describe common and less common CT findings 2. Identify PET/CT features and understand its added value and limitations 3. Recognize sarcoid reaction seen in oncological patients who underwent chemotherapy and sarcoidosis-lymphoma syndrome 4. Describe the importance of collaborative interpretation of CT and PET/CT

Results: Collaborative interpretation of imaging modalities is critical to narrow the differential diagnosis when there are less common/atypical findings of sarcoidosis in combination with avid FDG uptake. PET/CT can be useful for the staging and identification of occult sites and sites suitable for biopsy and for the assessment of inflammatory active sarcoidosis in patients with prolonged symptoms.

Conclusion: It is imperative for radiologists to be aware of the various imaging appearances of sarcoidosis and understand the added value as well as limitations of FDG PET/CT.