What are neuroblastomas?
Related conditions: Ganglioneuroblastomas, ganglioneuromas
Definition: Neuroblastomas are cancers, most often found in infants and young children, that grow from primitive, embryonic nerve cells. In 2014 the American Cancer Society (ACS) reported that one-third of tumors begin in the adrenal glands and one-fourth in the sympathetic nervous system ganglia, with growth in the abdomen. The remainder of neuroblastomas grow in the chest, neck, or pelvis, but all evolve from sympathetic nervous system ganglia.
Risk factors: Heredity may play a role in some neuroblastomas and is the only known risk factor. Infants with the familial form of neuroblastoma usually have a parent or someone in the family who had a neuroblastoma as an infant, and familial cases are usually diagnosed at a younger age. When familial neuroblastoma develops, there may be two or more tumors in various organs in the body. It is necessary to differentiate metastasis from multiorgan familial neuroblastoma.
Etiology and the disease process: There is no known cause of neuroblastoma other than heredity, which, according to the ACS, is involved in only 1 to 2 percent of cases. Neuroblastoma may form before birth and is occasionally found by fetal ultrasound. Most tumors develop before five years of age. Tumors are generally found only as the cancer grows and causes symptoms by pressing on organs. The tumor has usually metastasized by the time of diagnosis, and metastasis to the bone is common. Most tumors are fast growing, but in rare cases, the tumor cells may die spontaneously (apoptosis), and the tumor disappears. Occasionally, the tumor cells may quit dividing and become normal ganglia. This causes the tumor to become a ganglioneuroma, which is benign.
Incidence: The incidence rate of neuroblastoma in children under fifteen years of age is 10.2 per million, with the median age at diagnosis being seventeen months, as pediatric oncologist John M. Maris noted in a 2010 NEJM review. Neuroblastoma may be slightly more common in boys than in girls. Pediatric surgeon Andrew M. Davidoff stated in his 2012 Seminars in Pediatric Surgery review that neuroblastoma accounts for 8 percent of cancers in children under the age of fifteen.
Symptoms: Common symptoms of neuroblastoma include fatigue; diarrhea; a swollen abdomen; difficulty breathing as the tumor gets larger or spreads to the chest area; dark circles under the eyes; pale or flushed, red skin; excessive sweating; bone pain or tenderness; rapid pulse; high blood pressure; poorly controlled movement of the extremities; or paralysis. Symptoms depend on the site of the tumor, and parents may notice or feel a mass in the abdomen, chest, or neck.
Screening and diagnosis: There is no screening test for neuroblastoma. If a family has a history of neuroblastoma, it is important to tell the pediatrician at the first visit. Parents should take note of any unusual lumps, swellings, or changes in bowel or bladder patterns, as the symptoms of neuroblastoma often manifest in this manner. The diagnosis of neuroblastoma begins with a careful physical examination, as masses may be palpated (felt) in the abdomen, chest, or neck. A twenty-four-hour urine test, blood work, and cytogenetic analysis to look for changes in chromosomes are done. A bone marrow aspiration or biopsy specimen may also undergo cytogenetic analysis and pathology review. Imaging tests may include ordinary x-rays, computed tomography (CT) scans, ultrasound, a magnetic resonance imaging (MRI) scan, and a positron emission tomography (PET) scan.
Once a diagnosis is made, staging neuroblastoma is important to determine the treatment needed. The first step is to determine if the tumor has spread to other parts of the body. Additional tests may be indicated, including lymph node biopsy or fine needle aspiration of fluid from a lymph node as well as imaging studies with dye injection or injection of a small amount of radioactive tracer material. Four stages are used to classify neuroblastoma: Stages 1, 2A and 2B, 3, and 4 and 4S. The higher the stage, the more extensive the disease and its spread. Neuroblastomas are categorized as low risk, intermediate risk, and high risk based on stage, with treatment determined by risk group.
Treatment and therapy: Because neuroblastoma is rare, treatment in a clinical research trial is recommended by the National Cancer Institute. Treatment for neuroblastoma is multimodal, which means that surgery, radiation therapy, chemotherapy, and in rare instances watchful waiting may be used. The higher the risk group, the more aggressive the therapy. Surgery is the initial treatment of choice to remove as much of the tumor as possible and to biopsy lymph nodes. Radiation therapy may be used, especially if part of the tumor has been left behind after surgery or if distant metastases exist. Chemotherapy is used to kill any cells remaining after surgery or to attack cells that may have spread elsewhere in the body. Patients may be watched carefully until a change in their condition indicates the method of therapy. A team will make the best treatment decisions for the child based on staging, location of the tumor, and other factors.
Prognosis, prevention, and outcomes: The prognosis for neuroblastoma depends on the age of the child at diagnosis, the stage of the disease, the site of the tumor, the size of the tumor, and the type of tumor cells. Infants do better than older children. According to the ACS, low-risk group survival at five years is more than 95 percent, intermediate group survival is 90 to 95 percent, and high-risk group survival is approximately 40 to 50 percent. Neuroblastoma cannot be prevented.
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