Predicting malignancy in mediastinal lymph nodes by endobronchial ultrasound: a new ultrasound scoring system

Endobronchial ultrasound (EBUS) is now widely used in patients with resectable non-small-cell lung cancer to sample mediastinal lymph nodes (LN) for preoperative staging. The aim of this study was to investigate prospectively the utility of six ultrasound criteria to predict malignancy in mediastinal LN.

EBUS was performed in patients with mediastinal lymphadenopathy irrespective of the underlying disease. The following criteria were expected to predict malignancy: short axis >1 cm, heterogeneous pattern, round shape, distinct margin, absence of a central hilar structure and high blood flow in a LN. A sum score prediction model for malignancy was built. If more than two criteria were present, LN was classified as high risk for malignancy. Moreover, interrater variability of two blinded investigators was evaluated.

Two hundred eighty-one LN in 145 patients were analysed. Forty-four percent of LN were found malignant, 10% revealed sarcoidosis, and 10% revealed tuberculosis. Interobserver agreement was very good. Positive predictive value was best for heterogeneity (73%), with a negative predictive value of more than 80%. The sum score resulted in an odds ratio of 15.5 if more than two criteria were positive (P < 0.00001).

The assessment of ultrasound criteria during routine EBUS examinations is feasible and reproducible with very good interrater agreement. If less than three of the described criteria are present, a LN has a very low chance of being malignant. The best single criterion to predict malignancy is heterogeneity. The introduction of the sum score of ultrasound criteria could potentially increase diagnostic accuracy.