The contribution of diffusion-weighted imaging to the diagnosis of benign and malignant cause of palatine tonsil enlargement

Objective: The study aims to discriminate underlying malignant or benign cause of tonsil growth in patients with palatine tonsil hypertrophy using diffusion weighted imaging and quantitative ADC values. Material and Method: The study was conducted with 54 hypertrophic palatine tonsils of 36 patients, who had a palatine tonsil hypertrophy diagnosis, according to clinical examination and conventional MR images of 1.5 T MRI taken throughout the neck between January 2015 and May 2019 in our hospital. Diffusion weighted images of three b values (1000 sec/mm2, 2000 sec/mm2, 3000 sec/mm2) were obtained. ADC maps were created and the images were evaluated retrospectively. ADC measurement was performed by means of ROI on hypertrophic tonsil. Histopathological diagnoses of hypertrophic tonsil were later identified and the diagnoses were classified as benign and malignant. ADC values of three b values of benign and malignant diagnoses were compared between pathologies. Statistical analysis of the data was performed through one-way ANOVA and Kruskal Wallis test using SPSS (version 25.0) program. The cutoff value was determined by ROC analysis. Statistically, p<0.05 was considered a significant difference. Results: Of the benign diagnoses, the mean ADC values of reactive lymphoid hyperplasia were 0.702 ± 0.107 x 10-3 mm2/sec, 0.613 ± 0.095 x 10-3 mm2/sec, and 0.556 ± 0.127 x 10-3 mm2/sec (mean ± standard deviation), respectively, at three b values (1000 sec/mm2, 2000 sec/mm2, 3000 sec/mm2). Of the malignant diagnoses, the mean ADC values of squamous cell carcinoma were 1.046 ± 0.131 x 10-3 mm2/sec 0.819 ± 0.110 x 10-3 mm2/sec, and 0.679 ± 0.087 x 10-3 mm2/sec (mean ± standard deviation), while the mean ADC values of lymphoma, another malignant diagnosis, were 0.821 ± 0.263 x 10-3 mm2/sec, 0.634 ± 0.099 x 10-3 mm2/sec, and 0.551 ± 0.128 x 10-3 mm2/sec (mean ± standard deviation), respectively. Conclusion: In our study, we were able to discriminate reactive hyperplasia of tonsil from the squamous cell carcinoma of the tonsil with high sensitivity and specificity. As a result, it was concluded that ADC measurement may be a complementary tool to routine imaging methods in the characterization of palatine tonsil lesions. Keywords: Palatine tonsil, Diffusion weighted imaging (DWI), ADC