Neuroblastoma

Neuroblastoma is a type of cancer that develops from embryonic neural crest cells. These are immature nerve cells that can be found in several areas of the body. It is the second most frequently occurring tumor in children, the most common type of cancer in infancy and the most common extracranial (outside of the cranium or  skull)  tumor in childhood. Ninety percent of the cases are children younger than 5 years old.

Etiology or Causes

The etiology or cause of neuroblastoma is not very well understood.  What we do know, however, is that cancer in general begins with a genetic mutation whereas normal, healthy cells will continue to grow and not respond to the body’s signal to stop growing. They will continue to grow and multiply indiscriminately. This accumulation of abnormal cells will grow into a tumor.  Neuroblastoma begins its journey in neuroblast, which are immature nerve cells in the fetus. As the fetus matures, these cells become a part of the nerve cells and fibers, as well as, part of the cells that comprises the adrenal gland. Most of these neuroblast will mature by birth, however, some remain immature. Those immature cells will either disappear or will form a tumor, known as a neuroblastoma. There isn’t enough evidence to suggest a familial component since only 1-2% of case have that genetic component to it.

Signs and Symptoms

The signs and symptoms of neuroblastoma is contingent upon the origin of the tumor and the extent of metastasis. The most common site of origin is the abdomen.  Symptoms seen are abdominal pain, change in bowel habits (diarrhea), swollen abdomen, a non-tender abdominal mass, vomiting, and swelling in the legs. If the tumor is located in the chest, you could have wheezing, chest pain, and changes to the eyes, including drooping eyelids and unequal pupil size. Other signs that are prevalent with this condition includes back pain, bone pain, fever, unexpected weight loss, lumps of tissue under the skin, dark circles around the eyes and protruding eyeballs.

Diagnostic Test 

A thorough health history is often the catalyst for obtaining a diagnosis of neuroblastoma.  The parents are usually the first to notice a swollen or asymmetrical abdomen. Your child will undergo a CT scan or MRI to determine the site of the tumor and evidence of metastasis.  A chest x-ray, a bone scan and a skeletal survey may be performed to identify metastasis. Bone marrow aspirations and biopsies are performed to determine if the disease has migrated to the bone marrow. Elevated levels of catecholamines or their metabolites, such as dopamine, homovanillic acid (HVA) and vanillylmandelic acid (VMA) can be found in the urine or blood in 90% of the cases of neuroblastoma.   Neuroblastomas can also be detected by the use of the mIBG scan (meta-iodobenzylguanidine).  This nuclear medicine scan involves the injection of a radioactive liquid substance into the veins. This radioactive material is taken up by the tumors in up to 95% of cases and can be visualized with the use of a special gamma camera. This sophisticated scan is also utilized to monitor response to treatment of the disease.

Staging of Neuroblastoma – Once a diagnosis of Neuroblastoma has been made, your child’s physician will want to know, if the cancer has migrated (metastasized) to other organs and the lymph nodes. This can be determined by a series of imaging test and biopsy. The test utilized will include x-rays, bone scans, CT (computerized tomography) scans, MRI (magnetic resonance imaging) and MIBG scans and the process is known as staging.  Staging of the tumor is important because it determines the prognosis and the course of treatment.

  • Stage I – Tumor is confined to an organ or structure of origin
  • Stage IIA – The tumor extends beyond the organ or structure, but not beyond the midline. No lymph node involvement
  • Stage IIB – The tumor extends beyond the organ or structure, but not beyond the midline. Lymph node involvement on the same side of the tumor
  • The tumor has metastasized beyond the midline including bilateral lymph node involvement.
  • Stage IV – The cancer has metastasized (spread) to bones, bone marrow, other organs  and distant lymph nodes
  • Stage IV S – This is a special category of neuroblastoma, that applies only to children less than 1 year of age.  Metastasis has occurred to one or more sites except for the bones.

Treatment and Prevention

The treatment for the disease is dependent upon the staging of the tumor. It can be as conservative as observation due to the fact that some neuroblastomas will disappear without treatment.  However, in most cases of neuroblastoma some form of treatment is required. What is so unfortunate about neuroblastoma is that once the diagnosis is made, in many cases, metastasis has already taken place. Therefore, the surgical removal of the tumor, as well as, chemotherapy is warranted.  Radiation therapy and stem cell transplantation are other treatment modalities that are used to combat this disease.  There are other treatment options that are new which include immunotherapy using monoclonal antibodies and tumor vaccine.

When to see a doctor

Contact your child’s doctor if your child has any signs or symptoms that worry you. Mention any changes in your child’s behavior or habits.

Prognosis

With the proper treatment, your child’s chance of survival is very good. However, it is contingent on where your child ranked in the classification of the disease. If your child was classified as having low or intermediate risk disease your chances of a favorable prognosis is good. Their course of treatment is milder and the chance of a post disease sequela is lessened.    A child with high risk disease (stage 3 and 4) has a guarded prognosis.  Many survivors of the disease have post disease sequela which could include hearing loss, thyroid function disorder, stunted growth, learning difficulties, behavioral problems, and a greater risk of secondary cancer.