[Application of endoscopic ultrasonography in the diagnosis of mediastinal lymph node metastasis].

OBJECTIVES: To calculate the rate of detection for mediastinal lymph nodes and to set up a criteria for the diagnosis of metastatic mediastinal lymph nodes in lung neoplasm by means of endoscopic ultrasonography (EUS). METHODS: In 21 patients with lung cancer who underwent preoperative EUS on mediastinal lymph nodes, 103 lymph nodes detected by EUS were resected and confirmed pathologically all. The difference between benign and malignant lymph nodes was analysed statistically. RESULTS: The rates of metastatic lymph nodes detected by EUS were significantly higher than these of non-metastatic lymph nodes (chi(2) = 11.752, P = 0.01) in levels 5, 7, 8, and 9 of mediastinal lymph node staging map (Union Internationale Contre le Cancer, 1997). The mean long and short axis of metastatic lymph nodes were significantly longer than those of non-metastatic lymph nodes (short axis: t = 4.541, P = 0.000; long axis: t = 3.278, P = 0.002). Metastatic lymph nodes showed some characteristic ultrasonographic features, including short axis >/= 1.0 cm, long axis >/= 1.5 cm, and clear boundary. According to the equation P((1)) = 1/[1 + e(-(-2.963 + 2.041 X1 + 1.681 X2))], the lymph nodes were assumed to be malignant when P((1)) >/= 0.5. The accuracy, sensitivity, specificity of this methods were 72.8%, 72.7%, 72.9% respectively, and were superior to those of CT for the same nods in levels 5, 7, 8 and 9 (chi(2) = 6.812, P = 0.013). CONCLUSION: EUS is an effective method of diagnostic evaluation of mediastinal lymph nodes of lung cancer.