Evaluation of mediastinal lymph nodes using [18] F-FDG PET-CT scan and its histopathologic correlation

ABSTRACT

To determine the efficacy of integrated 18 F-fluorodeoxy glucose positron emission tomography-computed tomography [18 F-FDG PET-CT] in the evaluation and characterization of mediastinal lymph nodes into benign and malignant pathology. Thirty-five patients with mediastinal lymphadenopathies without primary neoplastic or infective lung pathologies were included in the study. The lymph nodes were detected on contrast-enhanced CT scan of the chest. All patients underwent 18 F-FDG PET-CT scan for evaluation of mediastinal lymph nodes. Results of PET-CT were compared with histopathology of the lymph nodes and sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated. Statistical Analysis: The data were collected prospectively and analyzed using [SPSS Inc., Chicago, IL] 11.5 software. Histopathology results in 35 patients revealed tuberculosis in 12, sarcoidosis in 8, and lymphoma in 15. Maximum standardized uptake value [SUVmax] of the benign lymph nodes ranged from 2.3 to 11.8 with a mean +/- standard deviation [SD] of 5.02 +/- 3.26. SUVmax of the malignant lymph nodes ranged from 2.4 to 34 with a mean +/- SD of 10.8 +/- 8.12. There was a statistically significant difference between benign and malignant pathology [P<0.0059]. 18 F-FDG PET-CT has sensitivity of 93% and specificity of 40% with SUVmax 2.5 as the cutoff. We found the optimal SUVmax cutoff to be 6.2 as determined by the receiver-operator characteristic curve. With 6.2 as cutoff, the sensitivity, specificity, and accuracy were 87%, 70%, and 77%, respectively. In countries where tuberculosis and other granulomatous diseases are endemic, SUVmax cutoff value of 2.5 has low specificity. Increasing the cutoff value can improve the specificity, while maintaining an acceptable sensitivity