Primary mediastinal tumors are divided for the convenience of diagnosis and surgical approach into three compartments: anterior, middle, and posterior. Each compartment is specific for certain tumors. Rarely does a benign tumor arising in one compartment actively invade another unless it becomes so large in size that it occupies the neighboring space. Furthermore, each compartment has a different malignant potential attributable to the nature of the mediastinal tumors endemic to that space (Table 137-1). This chapter concerns benign mediastinal tumors of the anterior and middle mediastinum (Fig. 137-1); posterior mediastinal tumors are described in Chap. 138.
Table 137-1. Classification of Mediastinal Tumors and Cysts |Favorite Table|Download (.pdf)
Table 137-1. Classification of Mediastinal Tumors and Cysts
Thymic neuroendocrine tumors
Germ cell tumors
Immature teratoma (age >15)
Immature teratoma (age <15)
Teratoma with malignant transformation
Mature teratoma with immature elements <50% of the tumor volume
Nonseminomatous germ cell tumors
Mixed germ cell tumors
Multinodular substernal goiter
Substernal thyroid cancer
Parathyroid substernal adenomas
Parathyroid substernal cysts
Lymph node masses
Sarcoid hyperplasia of lymph nodes
Metastatic lymphatic enlargement
Esophageal duplication cysts
Mediastinal tumors are divided for the convenience of diagnosis and surgical approach into three compartments: anterior, middle, and posterior.
The differentiation between benign and malignant mediastinal tumors depends on three major factors: mediastinal location, patient age, and the presence or absence of symptoms.1,2 The pragmatic consequence of dividing benign from malignant mediastinal tumors affects not only overall survival and tumor recurrence but also treatment protocols and surgical approach. Surgical standards mandate the use of larger incisions for resecting malignant mediastinal tumors to prevent local metastasis and to account for factors of size, diffuse adherence, hypervascularity, and local invasion to adjacent structures.3 However, this is not the case for benign tumors, where the only constraints are patient safety and procedural morbidity. Once these parameters are met, there is greater freedom of choice as to surgical approach, and the only limitations are port placement and incision size, which must be designed to accommodate tumor removal.
Mediastinal tumors are more often benign than malignant (two-thirds are benign). However, tumor status is location-dependent, with malignant potential increasing as one progresses from the posterior to the anterior mediastinal compartment. In a large series of mediastinal tumors, the malignant potential was 59% for anterior mediastinal tumors, 29% for middle mediastinal tumors, and 16% for posterior mediastinal tumors.4
The age of the individual is also a factor ...