Role Of Diffusion-weighted MR Imaging In The Discrimination Of Benign And Metastatic Parotid Area Lymph Nodes In Patients With Nasopharyngeal Carcinoma

AIM: To assess the utility of apparent diffusion coefficient(ADC)value determined on diffusion-weighted MR imaging(DWI)to differentiate between benign and malignant parotid area lymph nodes(PLN)in patients with nasopharyngeal carcinoma(NPC).MATERIALS AND METHODS: Thirty nine consecutive patients with NPC with a total of 40 enlarged,biopised PLNs underwent conventional and DWI MRI scans at two separate b values of 0 and 800 s/mm~2 prior to histopathological examinations between September 2008 and August 2016 in Fujian cancer hospital.Thirty three PLNs were histopathologically confirmed to be metastatic while 7 PLNs were diagnosed as benign lymphadenopathy.ADC values for benign and malignant PLNs were measured on the Philip and GE Adw workstation and compared.Shapiro-Wilk test and Mann-Whitney U test were performed with the statistical software version SPSS17.0,a two-tailed P value of < 0.05 was considered to be statically significant.The receiver operating characteristic(ROC)curve analysis was used to evaluate the diagnostic accuracy and the optimal threshold level of ADC values for diagnosis of metastatic PLNs.The kappa value was measured respectively to assess the degree of agreement between the histopathological diagnoses and the ADC values,or imaging features of PLNs such as the minimal axial diameter,necrosis,regional grouping,extracapsular tumor spread on MRI.RESULTS: The mean ADC value for benign PLNs was markedly higher than that of malignant PLNs for NPC.Use of a threshold ADC value of 1.01×10-3 mm~2/s was associated with a sensitivity of 85.7% and a specificity of 72.7%,to differentiate benign from malignant PLNs(area under the curve: 0.84).A moderate agreement of was observed between the histopathological diagnosis and the threshold of ADC value(k value: 0.483).However,short axis diameter,necrosis,extracapsular spread,and regional grouping of PLNs on MRI showed only a fair agreement with the histopathological diagnosis(k value: 0.257,0.305,0.276,and 0.205,respectively).CONCLUSION: Diffusion-weighted MR imaging with ADC map may be a promising technique to differentiate metastatic from benign PLNs,which needs to be further investigated in a large cohort of patients with NPC.