Staging and Restaging Pediatric Abdominal and Pelvic Tumors
A practical radiology review of Staging and Restaging Pediatric Abdominal and Pelvic Tumors, focused on imaging findings, differential diagnosis, reporting points, and...
A practical radiology review of Staging and Restaging Pediatric Abdominal and Pelvic Tumors, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.
Neuroblastoma
- Most common extracranial solid tumor in kids
- Calcifications = key clue (80–90% on CT)
- Crosses midline, encases vessels (NOT invades)
- Intraspinal extension → think neuroblastoma (Wilms NEVER does)
- Image-Defined Risk Factors= everything → ≥1 IDRF = L2 disease
- MIBG imaging mandatory (FDG PET only if MIBG-negative)
- Diffuse liver mets → easy to MISS on US/CT → MRI + DWI saves you
- Stage MS: <18 months + skin/liver/BM mets → better prognosis
Easy-to-forget pitfall
- Below L2 vertebral level, intraspinal extension is NOT an IDRF
Wilms Tumor
- Most common renal malignancy
- Claw sign = renal origin
- Calcifications are uncommon (~10%)
- Invades vessels (renal vein / IVC thrombus) — not encasement
- Never goes in spinal canal
- SIOP vs COG → surgery timing differs (Europe vs US)
- Biopsy upstages to stage III (SIOP!)
Response clue
- Size may stay same ↑ necrosis = good response
- ADC ↑ after chemo = good prognosis
Hepatoblastoma
- Usually <3 years, non-cirrhotic liver
- AFP ↑ in 80–90%
- Calcifications common (~50%)
- Hypovascular, no hepatobiliary contrast retention
- LI-RADS NOT recommended in kids
PRETEXT pearls
- Based on tumor-free liver sections, not tumor size
- Caudate lobe = report separately
- During chemo → POST-TEXT, after surgery → STOP using PRE/POST-TEXT
Lymphoma
- Hodgkin: adolescents, contiguous nodal spread
- Nodes abnormal if >2 cm long axis or FDG-avid
- Bulky disease → X suffix = worse prognosis
- Spleen ≠ solid organ → use S suffix, not stage IV
- NHL: more aggressive, extranodal, GI tract involvement
- Aneurysmal bowel dilatation = classic NHL clue
Response
- FDG PET + Deauville score rules follow-up
Germ Cell Tumors (GCTs)
- Midline, gonadal or extragonadal
- Seminoma: solid, homogeneous, no cysts/calcifications
- Nonseminoma: fat + necrosis + cysts + calcifications
- AFP ↑ (yolk sac), β-hCG ↑ (choriocarcinoma)
Classic trap
Growing teratoma syndrome
- Mass grows
- Tumor markers normalize
- FDG PET negative
- Needs surgery, NOT chemo
Rhabdomyosarcoma
- Most common pediatric soft-tissue sarcoma
- Botryoid subtype = “bunch of grapes”
- MRI preferred (local extent + nodes)
- Fusion-positive (PAX3/7-FOXO1) = worse prognosis
- RECIST 1.1 standard — volumetric optional
- Lungs + bone marrow = common mets → CT chest + FDG PET
Pitfalls
- Size stability ≠ no response → look at necrosis + ADC
- Liver metastases (neuroblastoma) often invisible on CT/US
- Wilms ≠ biopsy unless atypical (you may upstage!)
- Use SAME modality for follow-up every time
Clinical use note
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