Due to both the precision of imaging and technical developments in needle placement and catheterization, interventional radiology has assumed an important role in the diagnosis and treatment of thoracic disorders. A host of procedures are available to diagnose and treat thoracic disorders: guided diagnostic and therapeutic thoracentesis; drainage of empyemas or noninfected pleural collections; drainage of lung and mediastinal abscesses; pericardial drainage; transthoracic biopsy of pulmonary, mediastinal, pleural, and hilar lesions; pleural sclerosis; treatment of pneumothoraces; esophageal and tracheobronchial stenting; removal of pleural foreign bodies; and brachytherapy.
Diagnosis by transthoracic biopsy is achieved in 70 percent to 90 percent of cases (90 percent for malignancy). The typical assortment of bronchogenic, metastatic, and less common pulmonary tumors (carcinoid, lymphoma) all may be diagnosed by percutaneous biopsy. Diagnostic biopsy of anterior mediastinal lesions can be performed endoscopically (via the bronchi or esophagus), surgically (by using mediastinoscopy or thoracoscopy), or percutaneously.
CT permits safe biopsy in many, if not, most cases of mediastinal and hilar lesions. With current high-resolution CT, biopsy specimens of most hilar and mediastinal lesions larger than 1 cm may be obtained under CT guidance. Biopsy specimens may be obtained from mediastinal lesions in the pretracheal, aorticopulmonary window, and subcarinal regions, from pericardial and diaphragmatic nodes, and from lesions in the anterior, middle, and posterior mediastinum. Mediastinal and hilar biopsies permit staging of pulmonary malignancy, and may preclude unnecessary thoracotomy if a diagnosis of inoperability is made on the basis of the biopsy findings.
Percutaneous routes for biopsy of anterior mediastinal masses vary with the location of the lesion. "Protective" techniques can be used to establish windows and are in specimen retrieval. "Iatrogenic controlled pneumothorax", allows the lung to fall away from the mediastinal parietal pleura to avoid puncturing the lung. Saline injections "Salinomas" are used to increase the soft tissue mediastinal space allowing safe extrapulmonary access for biopsy. Transsternal biopsy is another consideration to access anterior mediastinal lesions.12 The diagnostic accuracy of percutaneous biopsy ranges from 74.5 percent to 90.3 percent. The sensitivity of percutaneous biopsy of mediastinal lesions is high for metastatic disease and germ cell tumors, and increases for lymphoma if immunohistochemical cytologic methods are used.3,8,10,11 Transbronchial biopsy provides diagnostic-quality specimens in only 23 percent-32 percent of the cases.1.2.4 Cervical and transthoracic mediastinoscopy yield positive results in 74.5 percent of the cases.6 Biopsy specimens of anterior mediastinal lesions can also be obtained surgically through mediastinoscopy or endoscopic thoracostomy. Cervical and transthoracic mediastinoscopy yield positive results in 74.5 percent of the cases.
Bronchoscopy can obtain a tissue or cytologic diagnosis, as well as assist in determining the anatomic location of tumors in the large airways. Bronchoscopic guided transbronchial needle aspiration biopsy (WANG needle) technique is an option for staging lymph nodes. Needle aspirates of the subcarinal lymph nodes (station 7) can reliably be obtained.9
Mediastinoscopy compliments fiberoptic bronchoscopy and FNA ± core biopsy in the assessment of mediastinal adenopathy. The mediastinoscope permits visualization of the anterior pretracheal space, carina, and anterior mediastinal lymph nodes. Mediastinoscopy allows direct biopsy of pretracheal (N2) nodes and can be performed when lymph nodes are determined to be >1 cm in diameter on CT. Cervical mediastinoscopy specifically accesses the left and right paratracheal lymph nodes (levels 2R, 4R, 10R, 2L, 4l, and 10L) and the subcarinal lymph nodes (level 7). In left upper lobe cancers, AP window lymph nodes (levels 5 and 6) represent the first N2 nodes11 and resection may improve survival. Although these extended mediastinoscopy techniques are advocated by some, we prefer CT guided FNA.
Video assisted thoracoscopy (VATS) can also be used in staging lung cancer and has the advantage of a panoramic view of the ipsilateral hemithorax while limiting surgical trauma and postoperative pain associated with thoracotomy.5 A disadvantage of thoracoscopy is that it is usually performed under general anesthesia using single lung ventilation. When a primary tumor <3 cm exists, thoracoscopy can provide an excisional biopsy for tissue diagnosis. Thoracoscopy also allows staging of the ipsilateral hilum and paratracheal lymph nodes. In the right hemithorax, the paratracheal lymph nodes cephalad to the azygous vein (levels 4R and 2R) and the "azygous" node can be visualized and biopsied. In the left hemithorax, the lymph nodes in the preaortic (level 6) and subaortic (level 5) spaces, and posterior mediastinum near the distal left mainstem bronchus can be visualized and biopsied. In both hemithoraces, the inferior pulmonary ligament lymph nodes (level 9) can be biopsied. Thoracoscopy can also confirm pleural studding in tumors with lymphatic invasion (i.e. diffuse bronchoalveolar carcinoma).
Endoscopic ultrasound can be used to identify and guide transesophageal needle aspiration of periesophageal and periaortic posterior mediastinal adenopathy. Although availability is limited and operator dependent, some report the ability to access enlarged nodes several centimeters away from the esophagus.
Mediastinal transthoracic needle aspiration biopsy (TNAbx) ± core bx as a minimally invasive alternative to mediastinoscopy was performed with CT (82) or ultrasound (7) guidance at UTMB in 89 patients from 1994-1998 with mediastinal lymphadenopathy or masses by CT imaging. Innovative "protective" techniques to establish access windows included iatrogenic pneumothorax (10) and saline injection, "salinomas" (11). Mediastinal TNAbx was used alone in 39/89, core bx was added in 49/89, and core bx alone in 1/89. Mediastinal TNAbx ± core was diagnostic in 69/89 (77.5 percent) with carcinoma diagnosed in 59/89 (61.8 percent). Specific diagnosis included cancer cell type, sarcoidosis, and caseating granulomas ± tuberculosis. TNAbx ± core of mediastinal lymph node stations readily accessible by mediastinoscopy [59] included anterior mediastinum (33), superior mediastinum (2), lower paratracheal (7), suprasternal (1), and lower pretracheal (1). Lymph node stations difficult or impossible to access by mediastinoscopy [35] included subcarinal (20), AP window (6), posterior mediastinum (6), parasternal (2), and periaortic (1). Pneumothorax occurred in 60 percent when traversing lung parenchyma was unavoidable and 10 percent when a "protective" technique was applicable: 20 percent of pneumothoraces required a chest tube with admission while 80 percent were observed and discharged from radiology. Of the 20/89 (22.5 percent) which failed to yield a diagnosis, all had mediastinoscopy with 11/20 (55 percent) found to have lung cancer: 16 were "negative" [8/16 true negative at up to four years follow-up, 8/16 subsequently false negative], 2 "suspicious" [one subsequently lymphoma, one true negative], and two "non-diagnostic" [both subsequently lung cancer]. In conclusion, TNAbx ± core bx of the mediastinum is diagnostic in approximately 80 percent of cases. A non-diagnostic biopsy therefore requires further efforts for a tissue diagnosis.
References
1. Gay PC, Brutinel WM. Transbronchial needle aspiration in the practice of bronchoscopy. Mayo Clin Proc. 1989;64:158-162.
2. Harrow EM, Oldenburg FA, Jr., Lingenfelter MS, Smith AM, Jr. Transbronchial needle aspiration in clinical practice. A five-year experience. Chest 1989;96:1268-1272.
3. Herman SJ, Holub RV, Weisbrod GL, Chamberlain DW. Anterior mediastinal masses: Utility of transthoracic needle biopsy. Radiology. 180:167-170, 1991.
4. Mehta AC, Kavuru MS,, Meeker DP, Gephardt GN, Nunez C. Transbronchial needle aspiration for histology specimens. Chest. 1989;96:1228-1232.
5. Mentzer SJ, Sugarbaker DJ. Thoracoscopy and video-assisted thoracic surgery. In Brooks DC., ed. Current techniques in laparoscopy. Philadelphia: Current Medicine, 1994;20.1-20.12.
6. Patterson GA, Piazza D, Pearson FG, et al. Significance of metastatic disease in subaortic lymph nodes. Ann Thorac Surg. 1987;43:155-159.
7. Pattison CW, Westaby S, Wetter A, Townsend ER. Mediastinoscopy in the investigation of primary mediastinal lymphadenopathy. Scand Jl Thorac Cardiovasc Surg. 1989;23:177-179.
8. Swanson DC, Wittich GR. CT-guided transsternal biopsy of a mediastinal mass. J Intervent Radiol. 5:163-164, 1990.
9. Wang KP, Haponik EF, Britt EJ, Khouri N, Erozan Y. Transbronchial needle aspiration of peripheral pulmonary nodules. Chest. 1984;86:819-823.
10. Weisbrod GL. Percutaneous fine-needle aspiration biopsy of the mediastinum. Clin Chest Med. 8:27-41, 1987.
11. Westcott JL. Percutaneous transthoracic needle biopsy. Radiology. 169:593-601, 1988.
12. Zwischenberger JB, vanSonnenberg E, Alpard SK, Goodacre B. Interventional Radiology in the Chest. In Yim AP, Hazelrigg SR, Izzat B, Landreneau RJ, Mack M, Naunheim KS., eds. Minimal Access Cardiothoracic Surgery. Philadelphia: W.B. Saunders, 1998.