The role Superb Microvascular Imaging (SMI) method in differentiation of axillary benign- malign lymph nodes

The role of Superb Microvascular Imaging (SMI) method in differentiation of axillary benignmalignant lymph nodes Objective: In this study, it is aimed to determine the contribution of vascularity index via SMI (Superb Microvascular Imaging) in axillary lymph nodes in addition to B-mode ultrasound (US) in the differentiation of malignant and benign lymph nodes. Material and methods: We performed a retrospective study between January 2020 and March 2022, at the Istanbul University Istanbul Medical Faculty, Radiology Department, Breast Imaging Unit. 155 patients, 170 lymph nodes were included in the study. Axillary lymph nodes examined in the study were divided into four subgroups as metastatic lymph nodes due to breast cancer, lymph nodes seen in granulomatous mastitis (GM), lymph nodes observed due to Covid-19 vaccination, and benign lymph nodes. In gray scale US examination, the largest diameter of the lymph nodes, short-long diameter ratio, cortical thickness, lymph node shape, and presence of fatty hilus were examined. Afterwards, the borders of the lymph nodes were marked by hand drawing in the SMI examination and the vascularity index was calculated automatically by the device. The data obtained from the gray-scale US and VI values were evaluated statistically and their diagnostic value was investigated. Results: In the gray scale US evaluation of the lymph nodes included in the study, increased cortical thickness, spherical shape, increased short-long diameter ratio, fatty hilum loss were found significantly higher in malignant lymph nodes compared to benign lymph nodes (p<0.05). In the SMI examination, mean and median VI values measured in malignant lymph nodes were found to be significantly higher than in benign lymph nodes (p=0.001, p<0.05). In the differentiation of malignant and benign lymph nodes, when the vascularity index cut-off value was set to 4.2% and higher, the sensitivity, spesificity, positive predictive value, negative predictive value was found to be 58.82%, 100%, 100%, 52.5% respectively. 4 When the VI value was used to differentiate GM-related lymphadenopathy and malignant lymph nodes, it was found to have higher specificity, positive and negative predictive value compared to Gray Scale US findings. Optimal cut-off value set to 5.2% for the vascularity index in the differentiation of metastatic and GM-related lymph nodes; sensitivity was 57.35%, specificity was 91.84%, positive predictive value was 90.70% and negative predictive value was 60.80%. Conclusion: Vascularity index values obtained with superb microvascular imaging would be beneficial to differentiate between malignant and benign lymph nodes. In addition, it is thought that high VI values observed in lymphadenopathies secondary to GM and vaccination can be used in the differentiation of malignant lymph nodes in appropriate clinical setting. In the evaluation of axillary lymph nodes, when gray scale US findings are combined with SMI, it has been shown that the diagnostic performance is increased in the differential diagnosis of axillary lymph nodes. Keywords: Lymph node, SMI, ultrasonograhpy, breast cancer, granulomatous mastitis