Neuroblastoma is derived from neural crest cells that form the adrenal medulla and the sympathetic nervous system. The cause is unknown. Most cases occur in young children, thus it is likely that neuroblastoma results from prenatal and perinatal events. Neuroblastoma may rarely (1% to 2% of cases) be hereditary. Mutations in the ALK and PHOX2B genes are associated with most familial cases. In sporadic cases, several genetic mutations have been identified.
Neuroblastoma is the most common extracranial solid tumor of childhood and the most common malignancy in infancy. The median age at diagnosis is 20 months. There are approximately 650 new cases of neuroblastoma in the United States each year. The incidence is estimated to be 1 in 7000 live births. The tumor usually occurs sporadically, but, in 1% to 2% of cases, there is a family history of neuroblastoma.
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Neuroblastoma is remarkable for its broad spectrum of clinical prognosis ranging from spontaneous regression to rapidprogression and metastasis resulting in death. Childrenwith localized disease are often asymptomatic at diagnosis,whereas children with metastases often appear ill and havesystemic complaints, such as fever, weight loss, and pain.The most common presentation is abdominal pain or mass.The mass is often palpated in the flank and is hard, smooth,and nontender. In the abdomen, 45% of tumors arise in the adrenal gland, and 25% arise in the retroperitoneal sympathetic ganglia. Other sites of origin are the paravertebralganglia of the chest and neck. Paraspinal tumors may invadethrough the neural foramina and cause spinal cord compression. Horner syndrome sometimes is seen with neck orapical masses. Several paraneoplastic syndromes, including secretory diarrhea, profuse sweating, and opsomyoclonus (dancing eyes and dancing feet), are associated with neuroblastoma.
Neuroblastoma may metastasize to multiple organs, including the liver, bone, bone marrow, and lymph nodes. Periorbital ecchymoses is a sign of orbital bone involvement. A unique category of neuroblastoma, stage 4S, is defined in infants (<1 year old) with a small primary tumor and metastasis limited to skin, liver, or bone marrow. It is associated with a favorable outcome.
A complete blood count and plain films may help identify patients with neuroblastoma. Calcification within abdominal neuroblastoma tumors is often observed on plain films of the abdomen.About 90% of neuroblastomas produce catecholamines (Vanillylmandelic acid; Homovanillic acid) that can be detected in the urine. Definitive diagnosis of neuroblastoma requires tissuefor light microscopic, electron microscopic, and immunohistologic examination. A computed tomography (CT) scan of thechest, abdomen, and pelvis; a bone scan and/or metaiodobenzylguanidine scan; bilateral bone marrow aspiration and biopsies;and urinary catecholamines complete the evaluation.
The abdominal presentation of neuroblastoma must be differentiated from Wilms tumor, which also presents as an abdominal flank mass. Ultrasound or CT examination usually differentiates the tumors. Periorbital ecchymoses from orbital metastases sometimes are mistaken for child abuse. Because children with bone marrow involvement may have anemia, thrombocytopenia, or neutropenia, leukemia is often considered in the differential.