Irregular Echogenic Foci Representing Coagulation Necrosis: A Useful But Perhaps Under-Recognized EUS Feature of Malignant Lymph Node Invasion

Abstract

Background: Coagulation necrosis has been described in malignant lymph nodes. Scattered irregular echogenic foci within a lymph node have been considered as more representative of coagulation necrosis as opposed to a normal central echogenic hilum in benign lymph nodes. Hence, our aim was to determine if coagulation necrosis in mediastinal lymph nodes imaged by EUS could be used as a useful echogenic feature for predicting malignant invasion. Methods: The data was collected retrospectively by reviewing cases of patients from May 2002 thru June 2005 with known or suspected lung cancer who underwent mediastinal lymph node staging by EUS at UTMB Galveston. An expert endosonographe (MSB) blinded to the final diagnosis, reviewed the archived digital EUS images of lymph nodes prior to being sampled by FNA. Lymph nodes positive for malignant by FNA were included. The benign group included lymph node images with either negative EUS FNA (or small benign appearing lymph nodes not subjected to EUS FNA) with subsequent surgical correlation of their benign nature. Results: A total of 24 patients were included. A total of 8 patients were found to have coagulation necrosis. Seven of the eight patients had a positive result for malignancy by EUS guided FNA. One patient determined to have coagulation necrosis had a non-malignant diagnosis indicating a false positive result. A total of 16 patients had no coagulation necrosis. Of the six cases, the final diagnosis was malignant and the remaining 10 cases, the final diagnosis was non-malignant. Sensitivity was 54%. Specificity was 91%. Positive predictive value was 88%. Negative predictive value was 63%. Accuracy was 72%. Conclusion: Coagulation necrosis described as scattered irregular echogenic foci within a lymph node is a useful test characteristic for staging mediastinal lymphadenopathy by EUS. Coagulation Necrosis has low sensitivity but high specificity. Coagulation necrosis when seen is a very useful echofeature that is highly specific when trying to differentiate benign from malignant lymph nodes on EUS. This feature may be particularly useful when EUS guided FNA cannot be done [e.g. peritumorous lymph node] or in selecting a lymph node for EUS guided FNA when multiple nodes are visualized. This strategy may help increase the yield of EUS guided FNA and decrease the procedure time. Tabled 1Summary of Results Coagulation Necrosis Final Malignant Diagnosis Final Non-malignant Diagnosis Present 7 1 Absent 6 10 Sensitivity 0.54, Specificity 0.91, Positive predictive value 0.88, Negative predictive value 0.63, Accuracy 0.71 Open table in a new tab Sensitivity 0.54, Specificity 0.91, Positive predictive value 0.88, Negative predictive value 0.63, Accuracy 0.71