Malignant cervical lymphadenopathy: Diagnostic accuracy of diffusion-weighted MR imaging

Purpose: To prospectively determine the diagnostic accuracy of diffusion-weighted magnetic resonance (MR) imaging for discrimination of malignant neck nodes due to lymphoma, squamous cell carcinoma (SCC), and undifferentiated nasopharyngeal carcinoma (NPC), with histologic findings and imaging criteria as reference standards. Materials and Methods: Ethics committee approval and informed consent were obtained. Patients with malignant lymphadenopathy underwent 1.5-T diffusion-weighted MR imaging. A region of interest was drawn around the malignant node on apparent diffusion coefficient (ADC) maps; ADC values were compared (Kruskal- Wallis test). Receiver operating characteristic analysis was employed to investigate whether ADC values could aid in discrimination among malignancies. Results: Forty-three patients (34 men, nine women; mean age, 54 years) with 43 nodes underwent imaging. Mean ADC values for lymphoma (n = 8), NPC (n = 17), and SCC (n = 18) were (0.664 +/- 0.071 [standard deviation]) x 10(-3) mm(2)/sec, (0.802 +/- 0.128) x 10(-3) mm(2)/sec, and (1.057 +/- 0.169) x 10(-3) mm(2)/sec, respectively, with significant differences between SCC and lymphoma or NPC (P < .001) and between NPC and lymphoma (P = .04). To optimize sensitivity and specificity with equal weighting, ADC threshold values for distinguishing between SCC and NPC, between SCC and lymphoma, and between NPC and lymphoma were 0.894 x 10(-3) mm(2)/sec, 0.824 x 10(-3) mm(2)/sec, and 0.694 x 10(-3) mm(2)/sec, respectively. To produce a 100% specificity while sensitivity is maximized, the following ADC threshold values were obtained for prediction of differentiation between malignancies: (a) SCC versus lymphoma, greater than 0.824 x 10(-3) mm(2)/sec (sensitivity, 94%), and lymphoma versus SCC, less than 0.767 x 10(-3) mm(2)/sec (sensitivity 88%); (b) NPC versus SCC, less than 0.764 x 10(-3) mm(2)/sec (sensitivity, 47%), and SCC versus NPC, greater than 1.093 x 10(-3) mm(2)/sec (sensitivity, 39%); (c) NPC versus lymphoma, greater than 0.788 x 10(-3) mm(2)/sec (sensitivity, 53%), and lymphoma versus NPC, no suitable threshold value. Conclusion: Diffusion-weighted MR imaging shows significant differences among malignant nodes of SCC, lymphoma, and NPC. ADC threshold values can help distinguish SCC from lymphoma.