thoracic neuroblastoma
description
neuroblastomas arise from cells which have their origin in the neural crest.
as a result, the sympathetic ganglia give rise to 30% of lesions which may occur in the thorax, abdomen, pelvis or head and neck. the remaining 70% of lesions arise from the adrenal medulla.
most cases are sporadic in nature, however occasional reports with a familial pattern suggest an autosomal dominant inheritance.
diagnosis
the common features are those of a solid well-defined rapidly growing paraspinal, intrathoracic mass which may have areas of central necrosis or calcification.
the association with metastases in the liver, placenta/cord or bone elevates the index of suspicion regarding the diagnosis.
the presence of elevated levels of maternal urinary vinillyl mandelic acid and homovanillic acid in association with maternal symptoms of sweating, flushing, palpitations or hypertension is seen in those few cases in which the fetal tumour is metabolically active.
malformations have occasionally been seen in association with neuroblastomas. these include absence of the corpus callosum, microcephaly, hydrocephaly, cardiac malformation, cleft lip and tracheo-oesophageal fistula. however, no consistent pattern of associated anomalies has been demonstrated.
peripheral neuroblastic tumours (including neuroblastomas, ganglioneuromas, phaechromocytomas, and paragangliomas) have been reported in association with congenital heart defects.
differential diagnosis
the differential diagnosis of intrathoracic fetal neuroblastoma includes the following:
- retroperitoneal teratoma does not normally appear as a paraspinal mass but is of mixed echogenicity.
- pulmonary sequestration is a solid echogenic unilateral triangular or conical mass whose aberrant blood supply can be demonstrated using colour doppler techniques.
calcification is not a feature of this lesion. the low impedance pulsed doppler waveform associated with a neuroblastoma is not associated with either lesion. if a liver mass is also present (metastases), a hepatoblastoma should be considered.
sonographic features
- posterior mediastinal mass arising in the paravertebral space.
- solid tumour but cystic areas can be present along with coarse and granular calcification.
- usually seen in third trimester.
- on serial assessment rapid change in size can occur.
- a solid liver mass indicates metastases which may also occur in placenta, bone or umbilical cord.
- oesophageal and cardiac displacement is associated with large tumours.
- hydrops fetalis and polyhydramnios are seen with liver metasteses and with vascular compression.
- low impedance pulsed colour doppler waveforms
associated syndromes