REMOVAL OF MEDIASTINAL TUMORS
Tumors of the mediastinum are a challenging group both diagnostically and in terms of treatment. A host of pathologic entities is involved, and for many of these, surgical excision is the treatment of choice. Recognition and identification of mediastinal abnormalities are almost always based on chest radiographs. Although the radiologic appearance is sometimes characteristic or (rarely) pathognomonic, most often it is the location within the mediastinum that is most influential in correct diagnostic interpretation.
Radiologic evaluation of the mediastinum depends on
computed tomography (CT) imaging of the chest. If the chest, on lateral view,
is divided into three roughly equal compartments in an anteroposterior plane,
the most common tumors are as follows: (1) anterior/superior mediastinum thymoma,
germ cell tumors (mature teratoma, teratocarcinoma, yolk sac tumor), lymphoma,
and intrathoracic thyroid extension (including substernal thyroid); (2)
middle/visceral mediastinum congenital bronchopulmonary foregut cysts and
tumors of lymphoid involvement (Hodgkin and non-Hodgkin lymphomas and
metastatic cancer); and (3) posterior mediastinum tumors of neurogenic origin
(neurofibroma) and esophageal lesions. Vascular tumors (aneurysms, anomalies,
angiomas) may occur anywhere in the mediastinum.
The likelihood of malignancy is based on the location,
the age of the patient, and the presence of symptoms. Two-thirds of mediastinal
tumors are benign, but those in the anterior compartment are more likely to be
malignant. The peak incidence of primary malignancy located in the mediastinum
is between the second and fourth decades of life. Patients presenting with
symptoms (localized or generalized) have a malignant process 85% of the time.
Most middle visceral and posterior compartment
mediastinal tumors can be approached surgically by the standard posterolateral
incision with the hemithorax entered at an appropriate level on the side of
maximal projection of the lesion.
The illustration shows removal of a neurofibroma, the most
common mediastinal tumor, which, characteristically, hugs the posterior
costovertebral angle. Most such tumors are readily shelled out, and their blood
supply is easily identified. The presence of an intraspinal component
(“dumbbell” tumor) should be ruled out preoperatively by means of magnetic
resonance imaging of the spine showing the intervertebral foramina. If present,
a collaborative procedure with a neurosurgeon is necessary to control the
intraspinal component, first avoiding potential cord compression or injury.
Although an anterior mediastinal lesion can be handled by
the lateral approach, most surgeons prefer a median sternotomy, as shown. This
is the preferred incision for thymic tumors, particularly in the presence of
myasthenia gravis in which complete extirpation of all components of thymic
origin is desired. When the tumor is large or densely adherent, this approach
may present difficulties because the tumor lies between the operator and the vital
structures from which it must be freed. A partial sternal splitting incision
extended into an anterior thoracotomy (hemi-clamshell) or bilateral transverse
sternothoracotomy (full clamshell) incision, on the other hand, is now quite
commonly used (for bilateral lung transplantation), is reasonably rapid, and affords
access to both pleural cavities.
