Pediatric Non-Hodgkin Lymphoma: Imaging Spectrum and Staging Pearls

A practical radiology review of Pediatric Non-Hodgkin Lymphoma: Imaging Spectrum and Staging Pearls, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Overview

• NHL = 7% of pediatric malignancies.
• CAYA (Children, Adolescents, Young Adults) → distinct subtypes, presentations, outcomes.
• Major histologic types: Burkitt (40%), lymphoblastic (30%), DLBCL (20%), ALCL (10%).
• Pediatric staging: St. Jude / IPNHLSS (extranodal disease focus).

Imaging Modalities

• US/CT/MRI = anatomic evaluation; PET/CT adds metabolic info.
• DWI MRI → high signal + low ADC (cellularity marker).
• WB MRI (STIR/DWI) = radiation-free alternative for staging & follow-up.
• PET/MRI → ↓ radiation ~80%, “one-stop-shop” hybrid imaging.

Abdomen & Pelvis Findings

》GI tract → Burkitt & DLBCL predominate; ileocecal region; aneurysmal bowel dilatation; intussusception possible.

》Liver/Spleen/Kidneys → multifocal low-enhancement lesions; DLBCL, HSTCL; PET = hypermetabolic foci.

》Ovaries/Testes → bilateral solid/cystic masses (Burkitt); testicular NHL = hypoechoic, hypermetabolic.

• 》Peritoneum → omental thickening, ascites, Burkitt-type in children.

Thoracic Involvement

• Mediastinum → 2nd most common primary site (thymic origin, not nodal); PMBCL in teens; risk of SVC syndrome.
• Lungs/Pleura → nodules, effusions; PET for pleural vs fluid distinction.
• Cardiac/Pericardial → rare; effusion or infiltrative masses (esp. post-transplant).

CNS Disease

#PCNSL (mostly DLBCL) → solitary > multifocal; frontal lobes, basal ganglia, corpus callosum.

#CT = hyperdense, minimal edema; MRI = iso/hypointense T1/T2, restricted diffusion, homogeneous enhancement.

• #Leptomeningeal/spinal → 17–18% involvement; enhancement on MRI.

Head & Neck Involvement

• Waldeyer ring → unilateral tonsillar or nasopharyngeal mass(DLBCL).
• Orbit → extraconal superotemporal mass, encasing globe.
• Mandible/maxilla (Burkitt endemic form) → lytic lesion with soft-tissue mass.
• Parotid/sinuses → homogeneous enhancing mass, may mimic infection.

Skeletal, Marrow, Soft Tissue

• ¤Bone → DLBCL most common; lytic lesion ± soft tissue; PET for staging.
• ¤Bone marrow → involved in 30–50%; FDG uptake patterns (diffuse, focal, mixed).
• ¤Muscle/Cutaneous → rare; T1 iso–T2 intermediate lesions; PET hypermetabolic.

Life-Threatening Scenarios

• Large mediastinal mass → airway/SVC compression (positional imaging critical).
• Intussusception/perforation → Burkitt-related; often surgical.
• Cardiac tamponade → pericardial effusion → urgent drainage.
• Rebound thymic hyperplasia post-chemo → mimic relapse (homogeneous, flexible).
• FDG pitfalls → G-CSF activation (↑ marrow/spleen uptake), steroid-induced uptake shift.
• Osteonecrosis → hypermetabolic false-positive bone focus post-therapy.

Key Pearls

• WB MRI = effective radiation-free staging tool.
• Pediatric NHL = predominantly extranodal; beware mimics (infection, IBD, sarcoma).
• Rapid diagnosis critical due to aggressive histologies but good chemo-sensitivity.
• PET/MRI & DWI emerging as future standards for pediatric lymphoma follow-up.