ARRS 2022 Abstracts


E1955. Compare and Contrast: Sarcoidosis, Sarcoid-Like Reaction, and Metastatic Mediastinal Nodes
  1. Ali Silver; University of British Columbia
  2. Omid Ebrahimzadeh; University of British Columbia
  3. Michaella Watson; University of British Columbia
  4. Tony Sedlic; University of British Columbia
Sarcoidosis, sarcoid-like reaction (SLR), and metastatic mediastinal lymph nodes can share similar imaging findings, but the correct diagnosis will have very different diagnostic, prognostic, and treatment implications. Understanding the similarities and differences between clinical presentation, patient demographics, pathophysiology, association with underlying pathologies, and imaging features of these entities can help radiologists in directing the appropriate care.

Educational Goals / Teaching Points
In this educational exhibit, we will conduct a multidisciplinary collaborative review of the pathophysiology of sarcoidosis including a discussion of clinical presentation and high-risk populations. We will explore common and uncommon imaging features of pulmonary sarcoidosis with case examples. We will define and illustrate the current understanding of SLR and review the association with malignancy, drug reactions, and clinical scenarios where it should be considered We will also compare and contrast imaging features of sarcoidosis, SLR, lymph nodes metastasis, and other mimics including opportunistic infections. Finally, we will provide direction for radiologists on when to consider SLR when sarcoid-type imaging features are present.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Pathogenesis of both SLR and “idiopathic” sarcoidosis remains unknown, therefore it is unclear if these are distinct immunopathologic entities, whether certain malignancies or drugs sensitize the immune system to develop sarcoidosis, or whether malignancy or drugs provoke underlying sarcoidosis. The common imaging findings associated with SLR include mediastinal, bilateral hilar lymphadenopathy, and perifissural lymph node enlargement or nodularity. These imaging findings are also seen in idiopathic sarcoidosis. Coming across these imaging findings in a patient with no history of sarcoidosis (intra\extra thoracic manifestations), particularly in patients who are not in the right demographic (i.e., > 75 years of age), should raise red flags for radiologists to think of SLR and its associated entities such as an underlying malignancy or drug-induced sarcoid reaction (DISR).

Although the jury is out on whether SLR is indeed a different entity from idiopathic sarcoidosis, it is important to be aware of entities such as cancer-associated SLR and DISR when reporting. Particularly, in older patients who present with new sarcoidosis-type radiologic findings, the radiologist should consider searching more carefully for a possible malignancy in the form of a suspicious nodule or chronic consolidation and adding cancer-associated SLR on the differential diagnosis. When new sarcoidosis-type radiologic findings are present, the radiologist can recommend medication review (in particular, if they are on cancer treatment). Recognizing DISR can lead to cessation of an offending drug that in a considerable number of cases can reverse the reaction.