How is a Neuroblastoma diagnosed?

Diagnosis depends on obtaining a tissue sample of the suspected tumour. A list of common criteria to diagnose the disease has been drawn up and is as follows:

A neuroblastoma is established if:

1. Unequivocal pathological diagnosis is made from tumour tissue by light microscopy (with or without immunohistology, electron microscopy, increased urine or serum catecholamines or metabolites).

or:

2. If a bone marrow aspirate or trephine biopsy contains unequivocal tumour cells (e.g. syncytia or immunocytologically positive clumps of cells) and increased urine or serum catecholamines or metabolites.

If a tissue sample is unobtainable then diagnosis is based on the infiltration of bone marrow, producing 'pseudorosettes' and increased catecholamine metabolite excretion. The measurement of vanillyl mandelic acid (VMA), homovanillic acid (HMA) and dopamine in the urine has a sensitivity of over 90% for detecting affected patients.

The extent of the disease must be evaluated in order to plan the appropriate form of treatment. The International Neuroblastoma Staging System (INSS) has provided guidelines for this purpose, and it advocates the use of CT and MRI to visualise primary tumours, and to examine that relationship to the local blood vessels. The bone marrow should be assessed histologically and morphologically, and immunocytological studies should be done on marrow aspirates. I132-MIBG and/or I123-MIBG to assess any bone involvement.

After a full assessment, the patient is assigned a stage number according to the guidelines set up by the INSS:

• Stages 1 and 2 describe a localised tumour
• Stage 3 is a tumour that invades across the midline or invades lymph nodes on the opposite side to the tumour
• Stage 4 is when metastases occur
• Stage 4s is a special stage that occurs in infants where the tumour tends to regress spontaneously.