Clinical History
A 6 weeks old male infant presented with nonspecific symptoms of vomiting and crying episodes, often seen in young children, and which usually settle with minimal intervention. However, clinical examination, together with radiological findings widened the possible diagnoses to include rarer conditions.
Imaging Findings
A 6 week old male infant, born at term, was brought to A&E with a 4 day history of non bilious vomiting following every feed. In addition, he had loose stools and episodes of inconsolable crying with drawing up of legs. On examination, he was apyrexic, well hydrated but irritable. Differential diagnosis was wide and included gastroenteritis, sepsis and pyloric stenosis. However, the non-specific nature of symptoms made it necessary to consider rarer conditions such as malignancy and metabolic abnormalities. The infant was commenced on intravenous antibiotics. Full blood count, urea and electrolytes and CRP were within normal limits. Blood, CSF and urine cultures were negative. The following morning a firm circumscribed mass was felt in the right side of abdomen. Ultrasound scan showed a 4.4 cm echogenic mass lesion, antero-inferior to the right kidney and anterior to the right psoas muscle. The differential diagnoses of the mass included neuroblastoma, teratoma and extra renal Wilms tumour. CT of chest and abdomen demonstrated a retroperitoneal enhancing mass with a clear fat plane around the lesion and no metastatic disease. Surgical intervention was planned for the earliest available theatre space. Laparotomy and complete excision of the retroperitoneal mass lesion was carried out. Histology confirmed neuroblastoma. Urinary catecholamines (sent prior to surgery) showed a raised dopamine/creatinine ratio. Subsequent isotope bone scan, Meta-iodo-benzyl-guanidine (MIBG) scan and bone marrow examination did not reveal metastasis. Post-operatively the infant is thriving and is under regular follow-up by the oncology team.
Discussion
Neuroblastoma is the third most common paediatric malignancy after leukemia and central nervous system tumours. It accounts for 8-10% of all paediatric malignancies, but, because of its aggressive nature, it accounts for 15% of cancer-related deaths in children. The median age at diagnosis is 2 years.
Neuroblastoma arises from primordial neural crest cells and can occur anywhere along the sympathetic chain or in the adrenal medulla. The most common primary site is the abdomen. Less common sites include posterior mediastinum, neck, and pelvis.
Neuroblastoma commonly presents as an abdominal mass with abdominal distension, however it may present with effects of metastases or with non-specific features including irritability, pyrexia and failure to thrive. The majority of children with neuroblastoma are clinically ill at presentation and approximately two thirds have metastases at initial diagnosis.
Most neuroblastomas secrete catecholamines (which can be detected in the urine) but rarely cause symptoms of catecholamine excess.
Ultrasound is generally the first line of investigation for an abdominal mass in the paediatric age group. The primary tumour and involvement of liver and kidney can be assessed by ultrasound. At ultrasound (US), most neuroblastomas are heterogeneously echogenic solid tumours with hypoechoic areas secondary to cystic necrosis or haemorrhage. Calcification is common and appears as focal echogenic areas (with or without distal acoustic shadowing) or diffuse increased echogenicity due to microcalcification.
CT is used for both local staging and to identify distant metastases. Most abdominal neuroblastomas are large and heterogeneous on CT, however small lesions may be homogenous. Calcification is seen in 80-90% of tumours.
MRI offers better soft-tissue contrast for local staging however tumour calcification may be difficult to detect. Intraspinal extension and intracranial (particularly meningeal) metastasis are best assessed by MRI.
Scintigraphic studies are useful in identifying the primary lesion and metastases. MIBG, an analogue of catecholamine precursor, labelled with iodine-123 or iodine-31, is taken up by both the primary tumour and metastases. However, a false negative scan may be seen in up to 30% of tumours (non-MIBG avid). MIBG is also less sensitive than isotope bone scan in detecting bone involvement. Isotope bone scan is therefore recommended in all patients to exclude skeletal metastases.
Differentiation between cortical and marrow disease is needed for staging. MIBG or isotope bone scan cannot provide this information. A bone marrow aspirate or biopsy is therefore required.
Total surgical excision is usually curative in stages 1 and 2. Chemotherapy is used for higher-stage disease. Follow-up imaging is determined by local imaging protocols.
The prognosis depends on the age at presentation, stage of the disease and tumour genetics. Neonates and infants have better prognosis compared to older children. Deletion of short arm of chromosome 1 and amplification of MYCN found on chromosome 2 are associated with poor prognosis. Up to 90% 3-year survival is seen in infants with stage 1 disease which falls to 15% in children (older than 1 year) with stage 4 disease.
Differential Diagnosis List
Extra-adrenal Retroperitoneal Neuroblastoma
Final Diagnosis
Extra-adrenal Retroperitoneal Neuroblastoma
