Differentiating Hodgkin Lymphoma and Sarcoid Reaction in Subsequent FDG-PET/CT: A Case Report and Literature Review.

Sarcoidosis is frequently associated with various hematological and solid tumors; it can be discovered by chance during tumor evaluations. Sarcoidosis can occur before some cancers, coexist with others, or be diagnosed 1 to 2 years later. Sarcoid reaction affecting hilar and mediastinal lymph nodes can pose a diagnostic challenge in patients with histopathological confirmation of Hodgkin lymphoma who are being evaluated using fluorodeoxyglucose-positron emission tomography computed tomography (FDG-PET/CT) scan because it cannot be easily distinguished from lymphoma infiltration. The presence of an increase or persistence of a prominent activity on a follow-up FDG-PET/CT scan after chemotherapy treatment for lymphoma that is associated with a complete metabolic response in the site of the primarily diagnosed lymphomatous disease is highly suggestive of concurrent sarcoidosis and necessitates careful assessment to avoid unnecessary therapy.