Evaluation of ¹⁸F-fluorodeoxyglucose uptake in enlarged mediastinal lymph nodes in patients with lung cancer

Accurate lymph nodal staging of lung cancer is critical for determining the treatment options. With the help of (18)F-fluorodeoxyglucose positron emission tomography/computer tomography ((18)F-FDG-PET/CT), the clinician can rule out/in the regional lymph nodes positive for metastasis in the patients with lung cancer in a majority of cases. However, a small proportion of cases with false positivity of metastasis have been reported. Transbronchial needle aspirations and mediastinoscopic biopsies are still necessary to determine whether enlarged hypermetabolic mediastinal lymph nodes are positive for lung cancer metastasis. Here we report three intricate cases showing hypermetabolic activity in the mediastinal lymph nodes in the patients with pathologically diagnosed lung cancer on PET/CT. The first patient had squamous cell carcinoma in the left upper lobe of the lung with surrounding necrotizing granulomas and concurrent with silicosis and granulomatous inflammation in the lymph nodes; the second presented with symptoms of viral pneumonia, which was pathologically diagnosed as a lung adenocarcinoma, stage IA, concurrent with sarcoidosis involving the lymph nodes; the last case was diagnosed as squamous cell carcinoma in the right upper lobe of the lung, but lymph nodes showed reactive hyperplasia. These cases suggest that some cases are so complex that avid (18)F-FDG uptake in the mediastinal lymph nodes in the patients with pathologically diagnosed lung cancer should be carefully analyzed based on individual patients' clinical background.