Pediatric Cancer Neuroblastoma

A neuroblastoma is a malignant tumor of the sympathetic nervous system. Arising out of primitive nerve cells, a neuroblastoma is the most commonly diagnosed cancer of infancy, with an incidence rate of one in 100,000 newborns. Approximately 500 new cases are reported every year in the United States.

The average neuroblastoma diagnosis occurs when a child 2 years of age. Caucasians appear to be more susceptible to neuroblastomas than other ethnicities. Overall, neuroblastomas account for eight percent of all childhood cancers.

The Sympathetic Nervous System and Neuroblastomas

The sympathetic nervous system is the part of the nervous system responsible for the body’s “fight or flight” response. The sympathetic nervous system includes nerve fibers along the spinal cord, the central adrenal glands and ganglia — clusters of nerve cell bodies found throughout the body. These nerve fibers secrete chemicals called adrenaline and noradrenaline. These are the chemicals that cause the heartbeat to increase, the blood pressure to rise and the pupils to dilate when the nervous system is under stress.

Neuroblastomas resemble so-called “primitive” nerve cells called neuroblasts. Neuroblasts are developing nerve cells and are usually seen in embryos and fetuses. In rare cases, neuroblastomas have been detected on ultrasound images of unborn fetuses.

Symptoms of Neuroblastoma

Neuroblastoma symptoms depend on which area of the sympathetic nervous system is affected. The tumor may be felt as a hard abdominal mass, or a mass in the pelvis, chest, head or neck.

Abdominal tumors can cause intestinal blockages, with accompanying pain. A chest tumor can cause breathing difficulties, while a neuroblastoma in the pelvic region can make urination difficult and cause constipation.

Other neuroblastoma symptoms can include diarrhea, irregular muscle contractions and hypertension (high blood pressure). If the tumor affects facial nerves, the infant or child may display opsoclonus (erratic eye movements) and Horner’s syndrome, where one eyelid droops and the pupil can’t dilate.

If the neuroblastoma spreads out of the nervous system, cancer cells are most likely to affect the lymph nodes, bone marrow and liver. Neuroblastoma metastasis, or spread, can produce symptoms such as:

  • back pain
  • bladder dysfunction
  • bone pain
  • bowel dysfunction
  • bruising of skin around the eyelids
  • fever
  • inadequate muscle tone
  • irritability
  • limping
  • low weight gain.

Neuroblastoma Diagnosis

Neuroblastomas occur most frequently in infants and young children. Most tumors are identified before the child is two years of age, and 90 percent of children with neuroblastoma are diagnosed by age five.

Various diagnostic tools are used to confirm the presence of a neuroblastoma. CT scans and magnetic resonance imaging (MRI) detect chest and abdominal tumors. Urine testing may detect the tumor cell markers homovanillic acid (HVA) and vanillylmandelic acid (VMA). In 90 percent of neuroblastoma cases, levels of HVA and VMA are unusually elevated.

Further testing to determine whether a neuroblastoma has metastasized beyond the nervous system may include a bone marrow biopsy and bone scan.

Neuroblastoma Treatment

Neuroblastoma treatment choices are determined by the child’s age, whether the cancer has spread to other organs and the location of the primary tumor. When possible, the tumor is removed surgically. Chemotherapy and radiation therapy are also used to kill cancerous nerve cells or shrink the tumor prior to surgery.

Neuroblastomas and Prognosis

In infants less than a year old, the prognosis is generally good, even in cases where the tumor has metastasized. An older child with a metastatic neuroblastoma has a less positive prognosis.

Five-year survival rates vary with age. A five-year survival rate means no sign of abnormal nerve cells can be detected five years after treatment, and the child is considered cured. Children less than a year old at the time of diagnosis have an 83 percent five-year survival rate. Children aged one to five have a 55 percent five-year survival rate, a figure that drops to 40 percent after age five.

Unusual Behavior in Neuroblastoma Nerve Cells

Neuroblastoma cells often act in ways that are different from those of cells of other types of tumors. Sometimes a neuroblastoma tumor will undergo apoptosis, or cell death, and the tumor disappears. Neuroblastoma cells have also been known to suddenly mature, transforming from abnormal, immature nerve cells into normal ganglion nerve cells. If this occurs, the cells stop reproducing and the neuroblastoma becomes a benign tumor.

Both sudden tumor cell death and cell maturation are unusual events, even for neuroblastoma tumors, and are more likely to occur in very small patients.

Resources

Children’s Cancer Web (2003). Neuroblastoma. Retrieved September 4, 2007, from the Children’s Cancer Web site: http://www.cancerindex.org/ccw/guide2n.htm.

National Cancer Institute (2007). General Information About Neuroblastoma. Retrieved September 4, 2007, from the NCI Web site: http://www.cancer.gov/cancerinfo/pdq/treatment/neuroblastoma/patient.

U.S. National Library of Medicine (2004). Neuroblastoma. Retrieved September 4, 2007, from the NLMMedlinePlus Medical Encyclopedia Web site: http://www.nlm.nih.gov/medlineplus/neuroblastoma.html.