Neuroblastoma is a cancer of specialised nerve cells, called neural crest cells. These cells are involved in the development of the nervous system and other tissues. Neuroblastoma can occur anywhere in the body, but it most often occurs in one of the adrenal glands, in the abdomen. In some children, the neuroblastoma occurs in nerve tissue alongside the spinal cord in the neck, chest, abdomen or pelvis. Neuroblastoma is the most common form of embryonal tumour. Embryonal tumours are characterised by the proliferation of tissue that is normally only seen in the developing embryo. They are mainly seen in very young children. The causes of neuroblastoma are not known. Incidence Neuroblastoma accounts for six per cent of childhood cancer registrations in the UK, with around 95 diagnoses annually. As with all embryonal tumours, neuroblastoma is most common in children under the age of 5 years and extremely rare after the age of 10 years. The incidence of neuroblastoma is highest in the under ones – it is the most frequent single type of cancer in the first year of life, accounting for one fifth of cancers in this age group. Neuroblastoma is slightly more common in boys than in girls, by a ratio of 6:5. Survival Neuroblastoma has one of the lowest survival rates of all childhood cancers, with only 67 per cent of patients surviving to five years. Neuroblastoma is also one of the few types of cancer for which survival differs significantly between the sexes – boys have a worse outlook than girls. Infants have a better outlook than older children: those diagnosed before the age of one year have five-year survival of 83 per cent compared to only 43 per cent for those in the 1 to 4 year age group. Staging of Neuroblastoma The stage of a cancer describes how far it has grown or spread. The stage is important because it helps determine the best treatment. There are four main stages of neuroblastoma: Stage 1 means the tumour is in one area of the body and hasn’t spread. It can be completely removed with surgery. Stage 2 is divided into 2A and 2B. In 2A, the tumour can’t be completely removed with surgery because of its size or position, but there are no cancer cells in any lymph nodes. In stage 2B, it may or may not be possible to completely remove the tumour, but it has spread to nearby lymph nodes. Stage 3 means that the tumour can’t be completely removed with surgery and there is either tumour on both sides of the body (either side of the spine) or there is tumour on one side of the body and lymph nodes containing cancer cells on the other. Stage 4 means that the cancer has spread to parts of the body that are some distance from where it started. Stage 4S is a special case, as it has a better outlook than other stages. Stage 4S means the child is younger than one year at diagnosis. The tumour may have spread to the liver or skin, but not to the bones. And no more than 10 per cent of cells in the bone marrow are neuroblastoma cells. Children with stage 4S disease almost always get better with very little treatment or none at all. These tumours either regress spontaneously or after chemotherapy, which is only given if the tumour is causing symptoms. They disappear completely or develop into a non-cancerous (benign) tumour, called a ganglioneuroma. Many of these children, after their initial diagnostic tests and staging investigations, will just need careful monitoring for some years. A newer staging system has been developed by the International Neuroblastoma Risk Group (INRG). This system looks at whether or not certain ‘image-defined risk factors’ are present in a neuroblastoma tumour before treatment. These risk factors can be detected by scans and help doctors understand the extent of the disease. Stage L1 – the tumour is localised and has not spread into vital structures nearby. It can be removed by surgery. Stage L2 – the tumour is localised but has ‘image-defined risk factors’ and can’t be safely removed by surgery. Stage M – the tumour has spread to other parts of the body. Stage MS – The tumour has spread to the skin, liver and/or the bone marrow in children younger than 18 months old. If the cancer has spread to distant parts of the body, this is known as secondary or metastatic cancer.