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The anterior mediastinum is the most common location of a thoracic tumor in
children. The “4 Ts” of the anterior mediastinal tumors include “terrible lymphoma,”
“teratoma,” “thymoma,” and “thyroid carcinoma.” The latter three are rare.
Nonmalignant conditions with AMM include adenopathy associated with infection,
sarcoid, and normal thymus. Common lymphomas ( Table 98.5 ) in the anterior
mediastinum include T-cell lymphoblastic lymphoma (or T-cell ALL with an
associated AMM), Hodgkin lymphoma, and diffuse B-cell large cell lymphoma.
Lymphoma can also occur in the middle mediastinum, which can also be the site of
masses associated with pulmonary sequestration and other developmental
anomalies. “Teratoma” of the mediastinum includes benign and malignant germ cell
tumors. Posterior mediastinal masses include neuroblastoma and other neurogenic
tumors such as malignant peripheral nerve sheath tumors (especially in patients with
neurofibromatosis, type 1), or benign lesions such as schwannoma.
Primary lung tumors are vanishingly rare in childhood but presentation of lung
metastasis at diagnosis or relapse is not uncommon. Many pediatric sarcomas, some
lymphomas, germ cell tumors, Wilms tumor, and rarely neuroblastoma can present
or recur with lung metastasis. These typically involve multiple small or large lung
nodules in the pulmonary parenchyma or are pleural based. Askin tumor is a unique
PNET chest wall tumor that occurs in children and young adults.

Clinical Considerations
Clinical Recognition
Tumors in the anterior and middle mediastinum often present with respiratory
symptoms ranging from mild cough to severe respiratory distress ( Fig. 98.1 ).
These tumors can compress the great vessels and cause SVC syndrome. When
asymptomatic they may be identified during evaluation for nonspecific systemic
symptoms or even discovered on a chest radiograph performed for another reason.
In contrast, posterior mediastinal masses are frequently identified on a chest
radiograph performed for another reason. They may, however, cause local pain from
nerve root involvement and/or cord compression (see “Tumors in and Around the
Spinal Cord” section).

The initial complaints associated with pulmonary metastasis may include
respiratory insufficiency, postobstructive infection, foreign body–type symptoms, or
hemoptysis. Pulmonary nodules may be discovered on a chest radiograph.
Pulmonary effusions can be the presenting sign of childhood cancer. Effusions
can be caused by malignant cells in the pleural space or from obstruction of
lymphatic drainage. Effusions are common with AMM due to leukemia or
lymphoma and can also occur with posterior mediastinal neuroblastoma, lung
metastasis, and chest wall tumors. They may be symptomatic or asymptomatic. The