Sarcoid-Like Reaction after Complete Remission of Malignancy: CT and (18)F-FDG PET/CT Features for the Differential Diagnosis from Lymph Node Metastasis

PURPOSE: To identify the imaging features indicative of sarcoid-like reactions in patients with intrathoracic lymphadenopathy after complete remission of malignancies. MATERIALS AND METHODS: This study enrolled five patients with histopathologically confirmed sarcoid-like reactions that developed after cancer remission. The clinical features and findings of CT and (18)F-fluorodeoxyglucose (FDG) PET/CT were assessed. RESULTS: The underlying malignancies included breast, nasopharyngeal, colon, and endometrial cancer and lymphoma. The time intervals between complete remission of malignancy and the diagnosis of sarcoid-like reaction ranged from 6 to 78 months. CT findings of sarcoid-like reaction included bilateral hilar and mediastinal lymphadenopathies (n = 5), pulmonary nodules (1–15 mm) with peribronchovascular, fissural, or subpleural distribution, and interlobular interstitial thickening in the lungs (n = 4). (18)F-FDG PET/CT revealed hypermetabolic uptake in the mediastinal and hilar lymph nodes and both lungs in the absence of extrathoracic uptake (n = 3). The sarcoid-like reactions resolved in all patients after corticosteroid treatment. CONCLUSION: In patients with complete remission of malignancies, newly developed bilateral hilar and mediastinal lymphadenopathies with or without pulmonary nodules of perilymphatic distribution, in the absence of recurrence at the primary tumor site and extrathoracic metastasis, may suggest a sarcoid-like reaction. Such cases warrant histologic evaluation of the lymph nodes to prevent unnecessary systemic chemotherapy.