Solitary fibrous tumor of the spinal cord

Last revised by Vincent Tatco on 27 Jul 2022

Solitary fibrous tumors of the spinal cord are uncommon spindle cell neoplasms of probable mesenchymal origin, most commonly arising from the spinal cord without dural attachment. 

They are histologically identical to solitary fibrous tumors located elsewhere, most commonly arising from the pleura. 

The remainder of this article largely focuses on solitary fibrous tumors arising from the spinal theca.  For a more general discussion of these tumors please refer to the article on solitary fibrous tumors of the dura

The median age at the time of diagnosis is 48 years 1. There is no reported sex predilection.

The most commonly reported presentations are back pain or radicular pain, and presentation is similar to other intramedullary or intradural masses. 

Solitary fibrous tumors of the dura were first described in 1996 and are rare. Prior to their classification as a distinct entity, solitary fibrous tumors were diagnosed as fibrous meningiomas or hemangiopericytomas.

Classically, solitary fibrous tumors are distinguished by the absence of any single diagnostic feature. The characteristic microscopic appearance is a "patternless" growth pattern, with bland spindle cell cytology, alternating hyper- and hypocellular areas, keloid-like hyalinization, and a frequently prominent branching vasculature often described as "hemangiopericytoma-like" 2. Myxoid changes have been reported in SFTs, particularly in the spinal cord lesions, but pure myxoid variants are extremely rare 3. Tumor cells stain positive for the stem cell marker CD34. Due to their histologic variability, solitary fibrous tumors may mimic other tumors 2.

Most cases of extrapleural SFTs are benign, however, malignant CNS solitary fibrous tumors have been reported 1. Histological features associated with “aggressive” extrapleural solitary fibrous tumors may be seen in up to 10% of extrathoracic tumors and include hypercellularity, moderate to- marked cytological atypia, necrosis, more than four mitoses per 10 high-power fields and/or an infiltrative margin 2. However, whilst these features are associated with clinical aggressiveness, they are not by themselves reliable predictors of such behavior. Like pleural solitary fibrous tumors, the behavior of extrathoracic tumors is unpredictable.

In contrast to intracranial solitary fibrous tumors which arise most frequently from the dura, spinal solitary fibrous tumors of the spinal cord are most commonly parenchymal (intramedullary) although both intradural extramedullary and intramedullary location is encountered 1,6. These intramedullary tumors do not, therefore, demonstrate a dural attachment 1. Intradural/ extramedullary and extradural extension of intramedullary lesions has been reported 7.

There are no specific appearances on CT. These tumors typically appear as relatively well-defined masses with heterogeneous enhancement. Rarely, calcification or necrosis may be visible 7.

Solitary fibrous tumors of the cord are usually well-circumscribed and encapsulated 3. Signal characteristics are typically:

  • T1 - isointense to hypointense
  • T2 - markedly hypointense
    • T2 hypointensity helps distinguish solitary fibrous tumors from other spinal cord tumors
    • T2 hypointensity is thought to be due to the presence of abundant collagen fibers 5
    • peritumoural edema may be seen
  • T1 C+ (Gd) - avid and homogeneous enhancement
  • spinal astrocytoma
    • hyperintense on T2 weighted images
    • ill-defined
    • patchy irregular contrast enhancement
    • eccentric location within the spinal cord
  • spinal ependymoma
    • hyperintense on T2 weighted images
    • hemorrhage is common
    • often associated with prominent cysts (tumoral and polar)
  • spinal ganglioglioma
    • hyperintense on T2 weighted images
    • mixed signal intensity on T1 weighted images
    • typically involve long segments of the spinal cord, often extending for greater than eight vertebral body segments
    • commonly eccentric in location
    • approximately half contain tumoral cysts
    • peritumoural edema is uncommon
    • patchy or no enhancement
    • calcification is common (low signal with blooming on GRE)
  • spinal hemangioblastoma
    • iso-hyperintense on T2 weighted images
    • focal flow voids on T2 weighted images
    • an associated tumor cyst or syrinx is common
    • hemosiderin capping may be present
  • spinal paraganglioma
    • hyperintense on T2 weighted images
    • usually located inferior to the conus
    • the characteristic “salt-and-pepper” appearance of neck and skull base
    • paragangliomas may be seen
  • spinal intramedullary metastases
    • hyperintense on T2 weighted images
    • extensive peritumoural edema

The prognosis of spinal solitary fibrous tumors remains unclear. The treatment of choice is complete surgical resection. Whilst this is curative in most cases, recurrence has been reported. The role of postoperative radiotherapy in atypical or incompletely resected CNS solitary fibrous tumors has not been established 1,5.

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