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Endobronchial ultrasonography with aspiration biopsy 
 of the mediastinal lymph nodes and video-assisted mediastinoscopic lymphadenectomy in detecting "occult" 
 N2-N3 metastasis in patients with non-small cell lung cancer

The condition of the mediastinal lymph nodes is an important factor in the selection of patients with non-small cell lung cancer for surgical treatment. Of particular concern are patients with not enlarged mediastinal lymph nodes according to CT-scan. The frequency of their “occult” pN2-N3 lesions can reach 22–41%. The aim of the study was to assay the possibilities of endobronchial ultrasono­graphy with transbronchial needle aspiration (EBUS/TBNA) of mediastinal lymph nodes and video-­assisted mediastinal lymphadenectomy (VAMLA) in detecting “occult” N2-N3 metastasis in patients with NSCLC. Materials and methods: 51 patients with proved NSCLC were included in this study. Inclusion criteria were: central tumor localization, peripheral cT2 tumors of more, cN1 stage, absence of mediastinal lymphadenopathy according to CT-scan. All patients performed EBUS/TBNA. Upon confirmation of the N2-N3 stage according to the data of a planned morphological study, the patient was referred to neoadjuvant therapy. With negative results, radical lung resection was performed. With inadequate results of an aspiration biopsy, VAMLA was performed with a frozen section study of one selective lymph node from stations 4R, 4L, 7. If their metastatic lesion was excluded in the same anesthesia, anatomical lung resection with systematic lymphodissection was performed. Results. The overall level of pN2-N3 lesion was 18.6% (9/51). Metastases to the mediastinal lymph nodes statistically prevailed in the group of patients with cN1 stage — 40% of cases (6/15). The fact of metastatic lesion of the lymph nodes did not depend on the adequacy of the aspiration biopsy. A metastatic lesion of the lymph nodes removed during VAMLA was revealed after the fact according to the results of a planned histological examination. The sensitivity of VAMLA was 71%, and PNV — 91%. Sensitivity and PNV of EBUS/TAB were 11% and 84%, respectively. Conclusion. cN1-stage is a factor of extremely high risk of "occult" metastasis. To exclude a regional lesion of not enlarged mediastinal lymph nodes, EBUS/TBNA is not enough. A necessary condition for the use of VAMLA in the framework of N-staging of patients with a high risk of “occult” metastasis is its use as an independent operation, with a mandatory planned study of all removed lymph nodes.