How is it assessed?
Investigations are likely to include the following:
Blood tests
- Full blood count (FBC).
- Liver function.
- Urea and electrolytes.
- Calcium.
- Lactate dehydrogenase (LDH).
- Serum Ferritin.
Bone marrow biopsy (to confirm or exclude bone marrow involvement)
Urine tests
- Spot urine collection for catecholamines and its metabolites (e.g. vanillyl mandelic acid or VMA) as these are usually produced by neuroblastoma cells and can be measured in the urine.
Imaging studies are very important and include -:
- CT scan.
- MRI scan.
- Metaiodobenzylguanidine (MIBG) scan – MIBG is injected in to the blood stream, is picked up by neuroblastoma cells and can show up the location of the primary tumour and any secondary sites.
Tumour biopsy is always performed unless the tumour can easily be removed, in which case initial resection of the tumour is performed. Tumour material is examined for genetic abnormalities; these can help in treatment planning by putting children in higher or lower risk groups. The genetic tests most commonly used are -:
- MYCN amplification status – There are 2 copies of the MYC gene in normal cells, but in neuroblastoma cells there can be multiple copies of the MYC gene. This is termed MYCN amplification and is detectable in tumour material. MYCN amplification only occurs in children with high risk disease.
- Ploidy – this term describes the number of chromosomes in the neuroblastoma cell nucleus. Diploid is normal and means there are two sets of chromosomes in each cell. Each chromosome is paired with another, making 46 chromosomes in 23 pairs. Triploid means there are three of each chromosome and hyperdiploidy means there are multiple sets of chromosomes in each cell. Hyperdiploid tumours are associated with a better prognosis.
Appearance of cells under the microscope – histology – ‘Shimada classification’ - is an assessment of the appearance of the neuroblastoma cells under the microscope. The appearance of the cells in conjunction with the child’s age correlates with outcome; some tumours look more malignant than others. Shimada classification divides children in to two groups: favourable and unfavourable and this classification based on appearance correlates with prognosis.
