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Chest Imaging

Neurogenic neoplasm, mediastinal

the most common cause of a posterior mediastinal mass, mainly in a paraspinal location. Neurogenic neoplasms may also arise in the other compartments of the mediastinum, the chest wall and occasionally the lung parenchyma. Pathologically these neoplasms can be divided into three main groups (Table 1).

Neurogenic neoplasm, mediastinal, Table 1. Classification of mediastinal neurogenic neoplasms.

Nerve sheath neoplasms
Neurofibroma thoracic / Neurofibrosarcomas
Schwannoma thoracic / Schwannosarcomas
Ganglion cell neoplasms
Ganglioneuroma mediastinal
Ganglioneuroblastoma mediastinal
Neuroblastoma mediastinal
Paraganglionic cell neoplasms (paragangliomas)
Chemodectoma
Phaeochromocytoma thoracic

Roughly 70% of neurogenic tumours arising in the chest are benign. Usually, they occur in younger patients, in the first four decades of life. Males and females are equally affected. Patients with neurogenic neoplasm are often asymptomatic, although these neoplasms may induce symptoms such as radicular pain and neurasthenia. Symptoms of cord compression may be present in case of intravertebral extension. Tumours arising from the peripheral nerves (intercostal) tend to be round in shape, and those arising from the sympathetic chains are usually fusiform with a more vertical orientation. On chest radiography, neurogenic neoplasms are seen as a sharply circumscribed homogeneous mass (Fig.1). Rib erosion with a sclerotic border is suggestive of a benign lesion. The presence of frank bone destruction or spread to multiple ribs is suggestive of malignancy. Calcification may be present in all types of neurogenic neoplasm.

On CT scans, neurogenic neoplasms typically appear as homogeneous soft tissue density although many of them have a low attenuation attributed to the lipid elements in the nerve sheaths or cystic degeneration. Due to their vascularization, they enhance after the administration of intravenous contrast medium. Relationships with vertebrae, ribs and the spinal canal are essential for planning therapy. Spinal involvement is particularly well assessed by using MRI. Multiplanar imaging helps demonstrate the longitudinal spread of the tumour along the spine. Widening of the neural foramina is often associated with nerve sheath neoplasm (Fig.2). Vertebral body erosion is mostly associated with sympathetic chain tumour. Generally benign neoplasms are homogeneous with well defined margins, whereas malignant neoplasms are mostly heterogeneous with irregular margins. On MR scans, neurogenic neoplasms appear as well-defined masses of homogeneous signal intensity appearing greater than that of skeletal muscle on T1-weighted images and markedly increased on T2-weighted images. They enhance following gadolinium administration homogeneously or inhomogeneously depending on various tissue components, vascularity or cystic degeneration (Fig.3).

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Fig.1

PA chest radiograph (a) and CT (b) showing a sharply circumscribed homogeneous mass abutting the right border of the heart which corresponds to a schwannoma of the right phrenic nerve.
Neurogenic neoplasm, mediastinal, Fig.1 (a)
Neurogenic neoplasm, mediastinal, Fig.1 (b)
Neurogenic neoplasm, mediastinal, Fig.2 (a)
Neurogenic neoplasm, mediastinal, Fig.2 (b)
Neurogenic neoplasm, mediastinal, Fig.3 (b)
Neurogenic neoplasm, mediastinal, Fig.3 (c)