Analysis of Endoscopic Ultrasound Elastography used for Characterization of Benign and Malignant Lymph Nodes

Background: Ultrasound elastography is a new imaging procedure that allows the reconstruc-tion of elasticity distribution by characterizing the difference of hardness between diseased tissue and normal tissue. Aim: The aim of our study was to apply real-time elastography during EUS examinations and to consequently characterize benign versus malignant lymph nodes. The pattern of real-time EUS elas-tography images was compared with the conventional EUS aspects of lymph nodes and with the final diagnosis obtained by EUS-FNA cytology analysis and/or by surgical pathology. Results: Patients diagnosed by EUS with cervical, mediastinal or abdominal lymph nodes were prospectively included, with a total number of 42 lymph nodes examined by EUS elastography. By using a qualitative pattern analysis we were able to differentiate benign and malignant lymph nodes with a high sensitivity, specificity and accuracy (91.7%, 94.4% and 92.86%, respectively), based on five pre-defined patterns obtained on EUS elastography. A quantitative analysis based on histo-grams of the EUS elastography images also allowed an excellent discrimination between benign and malignant lymph nodes. Based on separate RGB channel histogram values, an “elasticity ratio“ was further defined and yielded a sensitivity, specificity and accuracy for the differential diagnosis of 95.8%, 94.4% and 95.2%, respectively, based on a cut-off level of 0.84. Conclusions: EUS elastography is a promising method that allows the characterization and dif-ferentiation of benign and malignant lymph nodes with a high sensitivity, specificity and accuracy, offering complementary information added to conventional EUS imaging.