Endosonographic features predictive of malignancy in mediastinal lymph nodes in patients with lung cancer

Background: EUS is useful in determining mediastinal lymph node (LN) metastases in patients undergoing staging for lung cancer. However, FNA of LNs is often performed only if suspicious features are present. The utility of individual LN features in predicting malignant cytology remains unclear. Objective: To evaluate the utility of EUS-determined LN features for predicting malignant cytology. Design: Prospective observational study. Setting: Two U.S. tertiary-care centers. Patients: This study involved 425 patients with primary lung cancer who underwent EUS. Intervention: All mediastinal LNs were described according to size, shape, echogenicity, and margin characteristics. FNA was performed on LNs with any features suggestive of malignancy. EUS-guided FNA cytology was classified as benign or abnormal (suspicious/malignant). The utility of LN features in predicting malignant cytology was determined and further analyzed by logistic regression, and a predictive model was established. Main Outcome Measurements: Accuracy of individual LN features for predicting malignancy. Results: EUS detected 836 LNs in 425 patients, and FNA was obtained in 698 patients. On multivariable analysis, only round shape, a short axis of >8.3 mm, and sharp margins were predictive of malignant cytology. According to the predictive model, the calculated probability of having malignancy is less than 4% (95% confidence interval [CI], 0.022-0.064) when none of the LN features are present and 63% (95% CI, 51%-72.2%) when all features were seen. Limitations: No surgical histology as the criterion standard. Conclusion: Among patients with lung cancer, EUS features of round shape, sharp margins, and short axis of >8.3 mm are significant predictors of malignancy. The probability of malignancy is low when none of the features are present.