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.
