• Third most common extracranial solid tumor of childhood after leukemia and brain tumors, but cranial neuroblastomas are very rare
• Characterized by poorly differentiated neuroepithelial cells, groups of neurocytic cells and a variable neutropil rich stroma

• Sheets of densely packed primitive embryonal cells are seen in a lobulated pattern in a fibrillary background

• Occur at a wide variety of locations along the sympathetic chain
• Most common site is abdomen and pelvis (40% in adrenal medulla)
• Occur occasionally in mediastinum and neck and rarely in brain
• Diagnosed before 5 years of age with median age of 17.3 months

• Adrenal gland (40%)
• Abdominal and thoracic ganglia (40%)
• Cervical ganglia (5%)
• Rarely paratesticular and brain

• WHO grade IV

• Treatment modalities differ based on clinical subgroups, and include observation, surgical resection, chemotherapy, radiation therapy, stem cell transplantation, immunotherapy

Contributed by Nirupama Singh M.D., Ph.D. and Carmen Perrino, M.D.

• Ki67 is high in embryonal cells
• GFAP or synaptophysin for neural markers, also NB84 and neurofilament

• Pediatric small round blue cell tumors:
  • Lymphoma: CD45+
  • Primitive neuroectodermal tumor (PNET): CD99+
  • Rhabdomyosarcoma: desmin+
  • Wilm tumor: WT1+

A 2 year old patient presents with back pain and lower extremity weakness. CT scan demonstrates a paraspinal / dumbbell mass compressing the cord at L2. The most likely diagnosis is:

1. Ewing sarcoma
2. Lymphoma
3. Neuroblastoma
4. Wilms tumor

C. In this age group neuroblastoma is the most common of these tumors.

According to The International Neuroblastoma Pathology Classification, which features are prognostic factors for neuroblastoma?

1. Age, histologic classification and mitosis karyorrhexis index (MKI)
2. Age, tumor alveolar histology and DNA index (ploidy)
3. Age, tumor cell apoptosis and MYCN amplification
4. Age, tumor cell differentiation and necrosis

A. Prognostic variables for neuroblastoma include age, stage, and histologic classification, grade of tumor differentiation, MYCN status, and DNA index (MKI). Histology is graded according to the International Neuroblastoma Pathology Classification (INPC) which evaluates for degree of tumor cell differentiation and mitosis karyorrhexis index as related to age (less than or greater than 18 months) to define favorable or unfavorable histology.