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therapy when contralateral LNs and metastases are encountered. Unfortunately, cross‐sectional imaging with computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET) alone is not adequate to confirm a diagnosis; thus, a tissue sample is preferred. Recently, it has been suggested that the use of endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA) associated with endobronchial ultrasound‐guided transbronchial fine needle aspiration (EBUS‐TBNA) can adequately sample LNs in the mediastinum, avoiding the need for a futile surgery.

      The purpose of this chapter is to provide the basic anatomical information as well as technical maneuvers used to investigate the mediastinum successfully.

      EUS‐FNA is usually best suited to sample LNs adjacent to the esophagus which runs posterior to the trachea. Because of ultrasound artifacts created by the air‐filled trachea, lesions immediately anterior to the trachea are not well seen. EUS‐accessible stations include 2L, 2R, 4L, 4R, 5, 7, 8, 9, and, sometimes depending on the size, station 6. On the other hand, EBUS‐TBNA can target LNs either anterior or lateral to the trachea to the level of the carina, and alongside the left and right bronchial tree including stations 2L, 2R, 4L, 4R, 7, 10, and 11. Although both procedures overlap in stations 2 L/R, 4 L/R, and 7, in other stations they are complementary, and in combination allow nearly complete mediastinal access.

      EUS can use several types of needles: 19 gauge (G), 22 G, and 25 G for FNA, as well as Tru‐cut needles for core biopsy. The needle is occluded with a stylet during passage through the gastrointestinal tract wall and bronchial wall to minimize contamination from passage through those structures.

      EBUS equipment comprises a curvilinear array echoendoscope with an outer diameter of 6.7 mm and a biopsy channel of 2 mm. The ultrasonic frequency is 7.5 MHz with a penetration depth of 4–5 cm, making it well suited for FNA of LNs and lung masses through the trachea and bronchi. A 22 G needle is used to perform TBNA in the same manner as in EUS. Both systems have integrated oblique‐viewing optics to guide intubation and limited inspection.

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      The initial examination can be performed with either the radial or linear array echoendoscope; however, the linear scope is required to perform FNA. Given the obvious efficiencies, we prefer to use a single linear echoendoscope for both imaging and FNA.

      Linear scanning

Level Anatomical correlation
Superior mediastinal lymph nodes
1 Highest mediastinal
2 Upper paratracheal
3 Prevascular and retrotracheal
4 Lower paratracheal (including azygos nodes)
Aortic lymph nodes
5 Aortopulmonary (AP) window or subaortic
6 Para‐aortic (ascending aorta and phrenic)
Inferior mediastinal lymph nodes
7 Subcarinal
8 Paraesophageal (below carina)
9 Pulmonary ligament
N1 lymph nodes
10 Hilar
11 Interlobar
12 Lobar
13 Segmental
14 Subsegmental
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      Inferior posterior mediastinum

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