Value of diffusion-weighted MR imaging in the differentiation between benign and malignant cervical lymph nodes

Purpose: To evaluate echo-planar diffusion-weighted MR imaging (DWI) in the differentiation between benign and malignant cervical lymph nodes. Materials and methods: 35 consecutive patients with 55 enlarged (>10 mm) cervical lymph nodes underwent MR imaging at 1.5-T. DWI was performed using a single-shot echo-planar (SSEPI) MR imaging sequence with b values (b: diffusion factor) of 0, 500 and 1000 s/mm². Apparent diffusion coefficient (ADC) maps were reconstructed for all patients and ADC values were calculated for each lymph node. Imaging results were correlated with histopathologic findings after neck dissection or surgical biopsy, findings in PET/CT or imaging follow-up. Mann-Whitney test was used for statistical analysis and a receiver operating characteristic (ROC) curve analysis was performed. Results: Cervical lymph node enlargement was secondary to metastases from squamous cell carcinomas [n = 25], non-Hodgkin's lymphoma [n = 6], reactive lymphadenitis [n = 20], cat scratch lymphadenitis [n = 2] and sarcoidosis [n = 2]. The mean ADC values (×10^-3 mm²/s) were 0.78 ± 0.09 for metastatic lymph nodes, 0.64 ± 0.09 for lymphomatous nodes and 1.24 ± 0.16 for benign cervical lymph nodes. ADC values of malignant lymph nodes were significantly lower than ADC values of benign lymph nodes. 94.3% of lesions were correctly classified as benign or malignant using a threshold ADC value of 1.02 × 10^-3 mm²/s. Conclusion: According to our first experience, DWI using a SSEPI sequence allows reliable differentiation between benign and malignant cervical lymph nodes.