Neuroblastomas are pediatric tumours with primitive neuroectodermal differentiation and composed of immature neuroblasts. They are in the morphological category of “small blue cell tumours” and are thought to originate from primitive neural crest cells. Its peak incidence is between ages 0-4 years. The tumour occurs at sites with sympathetic neural crest derived tissue, most commonly in the adrenals. It presents often as an abdominal mass +/- pain and can be diagnosed with a combination of abdominal imaging, urine biochemistry for catecholamines, and histopathology.

The H&E image (see Related Content) shows a small round blue cell tumour with minimal cytoplasm. There are areas of neuropil and minimal schwannian stroma. There are also extensive areas of necrosis. The NB84 IHC image (this slide) shows positivity in the neuroblastoma cells.

The tumour is classified by the international neuroblastoma pathology classification system based on whether they are Schwannian stroma rich or stroma poor. Within the stroma poor category, they are further subclassified as undifferentiated (no neuropil), poorly differentiated (some neuropil, <5% differentiating tumour cells), or differentiating (>=5% of differentiating tumour cells, abundant neuropil). Major prognostic factors include age, stage, N-MYC amplification, favorable vs unfavorable histology, and ploidy.