Etiology of false-positive 18F-FDG PET/CT of mediastinal and hilar lymph nodes with surgical biopsy in cancer patients

Objective: This article aimed to describe the etiology of false-positive 18F-FDG PET/CT and its associations with clinical and imaging characteristics in cancer patients undergoing surgical biopsy of mediastinal and hilar lymph nodes at the Instituto Nacional de Cancerologia (INC), Bogota, Colombia, over a period of 8 years. Methods: Retrospective and analytical study. Results: In this study, 93 patients were included with a median age of 64 years (IQR: 55-70), and 57% were women. 35.5% of the patients had lung cancer, followed by lymphoma in 21.5%; 43% of the patients were smokers, and 17.2% had biomass combustion exposure. Of the 93 patients, 220 mediastinal and hilar lymph node stations were biopsied; 37 (16.8%) lymph node stations corresponded to false-positive 18F-FDG PET/CT. The etiology was anthracosis in 19 (51.4%) stations, sarcoidosis in 8 (21.6%) stations, negative for malignancy in 7 (18.9%) stations, and only two stations were granulomas. A statistically significant association was found between false positives and lymph node stations in patients >= 65 years (p=0.008) and patients with a history of smoking (p=0.021). In addition, an association was found between true positives and enlarged lymph nodes (p=0.033). Conclusion: The main etiology of false-positive 18F-FDG PET/CT was anthracosis. In contrast, granulomas were not an important etiology. An association was found between false positives and lymph node stations in patients >= 65 years and patients with a history of smoking. Association was also found between true positives and enlarged lymph nodes in the 18F-FDG PET/CT.