Clinical Presentation

A 9-year-old male presents to his family physician with a cough lasting a few days, shortness of breath with minimal exercise (worse when lying down), lethargy, chest pain, and intermittent fever. Patient is given antibiotics for possible pneumonia and is sent home. The child returns with persisting symptoms. A chest x-ray is ordered, which reveals a mediastinal mass.

Figure 109A

Figure 109B

Radiologic Findings

Mediastinal mass requiring biopsy subsequently confirmed lymphoblastic lymphoma.

Differential Diagnosis

The diagnosis of mediastinal masses in children may present a challenge. They are a heterogeneous group and may be of congenital, infectious, or neoplastic origin:

• Mediastinal lymph nodes are the most common source of mediastinal masses (including Hodgkin’s and non-Hodgkin’s lymphoma).
  
• Fatty masses: herniation of omental fat, mediastinal diffuse lipomatosis, lipoma, liposarcoma, and thymolipoma
  
• Cystic masses: usually congenital (foregut cysts), pericardial cysts, thymic cysts, lymphangiomas, intrathoracic meningocele
  
• Solid tissue masses: goiter (look for tracheal deviation in the upper mediastinum), hemangioma, parathyroid mass, Castleman disease, medullary cancer of the thyroid, thymic carcinoid, and metastasis of sarcomas and melanomas
  
• Germ cell tumor: benign teratomas (60%); malignant germ cell tumors are more common in males (teratocarcinoma, embryonic carcinoma, seminoma, endodernal sinus tumor, choricarcinoma, and mixed germ cell tumors).
  
• Neurogenic tumors are of three main types:
  
  
  
  • Nerve sheath tumors (common with neurofibromatosis): schwannoma and neurofibroma
    
  • Ganglion cell tumors (common in the pediatric population): neuroblastoma and ganglioneuroma
    
  • Paraganglionic cell tumors: paraganglioma and chemodectoma
  
  
• Post-transplant lymphoproliferative disease: children seem to be more susceptible; usually develops within 1 year of transplant.

Discussion

Background

A percutaneous core biopsy is a valuable tool in the diagnosis and pathologic characterization of a mediastinal mass. It is especially indicated if imaging suggests that the mass is invasive or unresectable. Four approaches have been used traditionally to biopsy mediastinal masses: parasternal, suprasternal, transpulmonary, and paraspinal. A transsternal approach also can be used in certain cases to biopsy mediastinal masses.

Etiology

Thymoma, neurogenic tumors, and benign cysts represent ~60% of mediastinal masses. Some differences exist between the adult and the pediatric populations. In adults, the most frequent lesions include primary thymic neoplasms, thyroid masses, and lymphomas. In the pediatric population, however, neurogenic tumors, germ cell tumors, and foregut cysts represent ~80% of all cases.

Clinical Findings