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MEDIASTINOTOMY AND MEDIASTINOSCOPY


MEDIASTINOTOMY AND MEDIASTINOSCOPY
Complete surgical resection is the key curative therapy for early-stage bronchogenic carcinoma. To be effective, resection must be performed under appropriate circumstances; not only must the patient be able to tolerate the required operation but the cancer must also be sufficiently well localized for complete surgical removal. Radical resection in the face of metastases to mediastinal nodes is rarely curative. For this reason, mediastinal nodal staging is essential. Cervical mediastinoscopy and left anterior mediastinotomy remain the gold standard for sampling mediastinal lymph nodes. These procedures may also aid in the diagnosis of lymphoma, sarcoidosis, and other diseases affecting the mediastinum.



Staging In The Management Of Lung Carcinoma
For modern thoracic specialists, the selection of patients for lung cancer operations involves a definition and an assessment of certain discriminating factors related to the primary tumor and its lymphatic and hematogenous metastases. In recent years, an effective and meaningful internationally vetted system for staging lung cancer has evolved (see Plate 4-49). Enlarged or hypermetabolic lymph nodes on computed tomography or positron emission tomography scan, respectively, are at risk of harboring metastatic cancer and require acquisition of tissue for definitive pathologic staging.

Surgical Evaluation Of The Regional Lymphatic System
Of particular interest is the surgical investigation of the lymphatic drainage of the lung (see Plates 1-30 and 1-31) as it relates to data collection for clinical staging before a pulmonary resection. The lymphatic drainage system provides distinct predictable routes or pathways for the spread of malignancies from each lobe of the lung to the hilum and up the mediastinum to the base of the neck. Usually performed under general anesthesia, a mediastinoscopy involves a horizontal suprasternal low cervical skin incision to expose the lower cervical part of the trachea. Through this, central cervical and medially located supraclavicular lymph nodes can be visualized and biopsies performed. The surgeon may also expose and digitally dissect the pretracheal space. Much information can be gleaned through initial palpation of the developed tract. Usually, the presence and location of enlarged lymph nodes, as well as the size, fixation, and relationships to neighboring structures, can best be identified by this means. After the pretracheal tract has been fully developed by preliminary digital exploration, the mediastinoscope is introduced to facilitate direct visualization and biopsy of nodal tissue. Although mediastinoscopy involves some risk of bleeding, information obtained may obviate the need for thoracotomy when resection for potential cure is clearly not feasible.
Debate continues regarding the indications for mediastinoscopy and how to interpret and use the information gained. Most physicians would agree that patients with clearly resectable clinical stage I cancers are unlikely to benefit from the examination. Almost all would concur that contralateral mediastinal lymph node metastases or any metastasis fixed to adjacent structures is not resectable. Less certain is the interpretation of ipsilateral, freely movable, intracapsular nodal metastases that might be included in a radical mediastinal lymph node dissection at the time of thoracotomy and lung resection. Still, current knowledge clearly defines mediastinal lymph nodal metastasis as stage III disease, and despite radical resection, fewer than 10% of patients will experience long-term survival. Most thoracic oncologists view stage III disease as a systemic process requiring combined modality therapy, usually not surgery, to improve survival.
Mediastinoscopy should not be performed in the presence of clinically palpable cervical or scalene lymphadenopathy. Direct surgical biopsy of these nodes can be accomplished at minimal risk, and if malignancy is present, inoperability is confirmed. Biopsy of the scalene nodes should not be carried out on patients with bronchogenic carcinoma when the nodes are not palpable. Furthermore, for a left upper lobe neoplasm, cervical mediastinoscopy is less often definitive inexcluding N2 disease and establishing operability than is the case for left lower lobe and right-sided tumors.
For left upper lobe lesions, the left anterior extrapleural mediastinotomy developed by Chamberlain has proved most helpful. Ordinarily, anterior mediastinotomy is accomplished through a horizontal incision over the second anterior costal cartilage. The surgeon exposes the mediastinal lymph nodes overlying the left pulmonary artery, phrenic nerve, and subaortic space and can readily perform a biopsy.
Recently, alternative means of sampling mediastinal lymph nodes have been developed. These include video-assisted mediastinoscopic lymphadenectomy (VAMLA) and endobronchial ultrasonography with transbronchial needle aspiration (EBUS-TBNA). VAMLA allows for complete resection and removal of pertinent lymph node stations. Although EBUS-TBNA has been gaining popularity, it has not been found to be as efficacio s as mediastinoscopy in routine mediastinal staging.