Question

What is the most common site of metastasis in a child with neuroblastoma?

• A. Brain
• B. Lungs
• C. Bone marrow
• D. Liver

Hint:

Neuroblastoma Metastasis Hierarchy:
$\bullet$ Most common metastatic site: Bone marrow ($>70\%$) $>$ Cortical bone $>$ Lymph nodes $>$ Liver.
$\bullet$ Lung and Brain metastasis are exceedingly RARE at presentation (unlike Wilms tumor, where lungs are the most common metastatic site!).

Answer 1

The Correct Option is C

Concept:
Neuroblastoma is the most common extracranial solid malignant tumor of childhood, arising from primordial neural crest cells destined to form the sympathetic ganglia and adrenal medulla.
Over $50\text{--}60\%$ of children present with advanced metastatic disease (International Neuroblastoma Risk Group Stage M) at the time of initial clinical diagnosis.
Explanation:
• Neuroblastoma exhibits a strong tropism for hematogenous and lymphatic dissemination to specific anatomical sites.

• The bone marrow is statistically the single most common site of metastatic involvement, detected in approximately $70\text{ to 80\%$} of children with metastatic disease.

• Cortical bone (metaphyses of long bones, skull, and orbits causing periorbital ecchymosis "raccoon eyes") is the second most common metastatic site ($50\text{--}60\%$).

• Distant lymph nodes and liver (e.g., Pepper syndrome in infants with massive hepatic infiltration) are other frequent metastatic locations.

• Pulmonary parenchymal (lung) and central nervous system (brain) metastases are distinctly rare at initial diagnosis, occurring in $<3\text{--}5\%$ of patients and typically only in advanced terminal relapses.

• Complete metastatic staging mandates bilateral posterior superior iliac spine bone marrow aspirates and trephine biopsies, alongside $^{123}\text{I-MIBG}$ scintigraphy.
Final Answer:
The bone marrow is the most common site of distant metastasis in pediatric neuroblastoma.