The false negative and positive of 18F-FDG PET/CT in regional lymph node of lung cancer

Objective: 18F-FDG PET/CT is now widely used in clinical staging of lung cancer. But false positive(FP) and negative (FN) results may occur. The aim of this study was to analyze the factors causing false 18F-FDG PET/CT results in the detection of lymph node in non-small cell lung cancer (NSCLC). Methods: Forty-eight patients underwent pulmonary lobectomy and dissection of lymph nodes after their 18F-FDG PET/CT and contrast enhanced CT results were retrospectively reviewed. The pathological status of the resected lymph nodes was the major concern. Results: The pathological examination confirmed metastasis in 51 out of 313 excised lymph nodes in 48 patients. There were 7 FN and 8 FP lymph nodes in PET/CT. The positive and negative predictive values of PET/CT were 85% and 97%, respectively, compared with 57% and 94% of CT(P=0.002, 0.045; respectively). Among the seven FN lymph nodes, 3 were with smaller tumor foci, 2 were 0.4 mm in short axis, and 2 proximate to the primaries were masked by the higher uptake of the primary tumor. The 8 FP lymph nodes were all with pulmonary complications and lymphadenitis. Conclusion: The smaller size, micro-metastases, and little separation from the primaries were the major reasons for FN, and the lymphadenitis with pulmonary complications for FP lymph node imaging in PET/CT. (authors)