spinal PNET

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Spinal primitive neuroectodermal tumors (PNETs) are rare. Most cases are secondary to metastatic spread through the subarachnoid space from a primary intracranial tumor although rare cases of primary spinal PNETs have been reported.

This article specifically relates to spinal PNETs. For a discussion on intracranial PNETs and for a general discussion of the pathology refer to the main article: CNS primitive neuroectodermal tumor (PNET).

Epidemiology

Unlike intracranial PNETs, those involving the spine are slightly more common in adults than in children. Males are more commonly affected than females.

Clinical presentation

Clinical presentation is similar to that of other intramedullary spinal tumors, with pain, weakness, and sensory changes common.

Pathology

PNETs are aggressive embryonal tumors. Histologically, they are composed of small round blue cells that are predominantly undifferentiated. There may be occasional differentiation along neuronal or glial lines . It has been postulated that PNETs arise from neoplastic transformation of primitive neuroepithelial cells in subependymal zones .

Radiographic features

Spinal PNETs may be intramedullary, extramedullary intradural or extradural in location. The most common sites of spinal involvement are the filum terminale and cauda equina (57%). Twenty-one percent occur in the cervical cord and 14% occur in the thoracolumbar area .

CT

May be normal .

CT myelography

Enlargement of the spinal cord with blockage of contrast .

MRI

Appearance on MRI is non-specific, often mimicking other spinal lesions .

Reported signal characteristics include :

T1: hypointense
T2: hyperintense
T1 C+ (Gd)
- diffuse heterogeneous enhancement
- because CSF seeding commonly occurs, leptomeningeal enhancement may be seen

Treatment and prognosis

Spinal PNETs are associated with a poor prognosis (50% survival rate at 2 years) .

Dissemination through the CSF may produce secondary intracranial deposits. Distant metastatic spread may also occur to lungs, bone, and lymph nodes .

Surgery and radiotherapy are regarded as first-line management for spinal PNETs. The use of chemotherapy has been inconsistent .

Local recurrence is common.

Differential diagnosis

myxopapillary ependymoma
- the enhancement pattern is typically homogeneous (however they can have a variable enhancement pattern that, in part, depends on the amount of hemorrhage present)
- prone to hemorrhage
astrocytoma
- more commonly located in the thoracic and cervical regions
- ill-defined
metastases
- extensive peritumoural edema
- more commonly located in the cervical and thoracic regions