Management of Mediastinal Mass in Infants

Initial Imaging Strategy

The American College of Radiology recommends chest radiography or MRI chest as equivalent initial imaging options for clinically suspected mediastinal mass, with MRI preferred over CT to minimize radiation exposure in infants 1, 2
For infants, MRI is strongly prioritized over CT to avoid radiation exposure, as pediatric patients are at inherently higher risk from radiation due to organ sensitivity and longer life expectancy 1, 2
Chest radiography can localize the mass to a specific mediastinal compartment and narrow the differential diagnosis 3

If chest radiography shows an indeterminate mass, proceed to MRI chest or CT chest as equivalent next steps, with MRI superior to CT for neurogenic tumors 1, 2, 3
MRI definitively distinguishes cystic from solid lesions, preventing unnecessary biopsy and surgery, and detects hemorrhagic and proteinaceous fluid, microscopic fat, cartilage, smooth muscle, and fibrous material 3
Diffusion-weighted imaging (DWI) can distinguish normal/hyperplastic thymus from thymic tumors and lymphoma in all age groups 3

Start non-intensive chemotherapy if diagnosis must be delayed due to sample transport to central laboratories, as in cases of suspected lymphoma 5
In infants with hyperleukocytosis or mediastinal mass causing compression, treatment can be started based on peripheral blood or bone marrow smear before definitive diagnosis 5

Image-guided transthoracic needle biopsy is appropriate when diagnosis cannot be definitively made by imaging, with core biopsy more effective than fine-needle aspiration 1, 2
DWI MRI can direct biopsy toward sites of higher cellularity and away from hemorrhagic necrosis 3, 6