Figure 1 a) Radiograph frontal view showing homogenous opacity lesion in the right upper and mid zone with broad base towards mediastinum. The lesion is causing shift of mediastinum and trachea to the contralateral side and compressing the trachea just above the carina (arrow head). The lesion is extending above the clavicle (cervico-thoracic sign) and erosion of posterior end of third and fourth ribs (Long arrow). C) Contrast enhanced CT scan axial section mediastinal window showing heterogeneously enhancing mass lesion in the right posterior mediastinum extending to middle mediastinum causing compression of the trachea. The lesion is showing multiple small foci of calcification (black arrows in fig c).
Primary mediastinal neuroblastoma accounts for 14% of all neuroblastomas. Common location is posterior mediastinum, where they arise from paravertebral sympathetic chain. Patient commonly present with chest pain, cough and respiratory distress due to airway obstruction. Chest radiograph is the initial radiological investigation to be done in such patients. It demonstrates homogenous opacity mass in the mediastinum. If the tumor is large, there may be extrinsic compression and displacement of trachea and main bronchus with mediastinal shift (fig a-c). Rib erosion and asymmetrical widening of inercostal spaces may be seen on radiograph. Intraspinal extension may be seen as loss of vertebral height with widening of neural foramina on lateral radiograph. Approximately 50% of the lesions show calcification on radiograph.
CT scan is usually done to confirm the presence of lesion, and it also helps to define the location and extent of lesion, adjacent organ involvement, or vascular involvement. CT demonstrates calcification in up to 90%. The lesion characterization has become better with the advent of multiplanar image reconstructions in MDCT. However MR imaging is the investigation of choice for better characterization and demonstration of full extent of mass, extradural intraspinal extension and chest wall invasion. The advantages of MR over CT are its direct multiplanar imaging and better contrast resolution, which can allow differentiation of vascular from non vascular lesions without the aid of intravenous contrast agent. MR is very often used to evaluate tumor involving spine and spinal canal.
Radiograph is the initial investigation to be done in the mediastinal masses and one should be able to identify the lesion and arrive at differential diagnosis. CT scan and MRI are done to confirm the lesion, location, extent, adjacent organ involvement or vascular involvement and intraspinal extension.