Calcifying pseudoneoplasm of the neuraxis

Calcifying pseudoneoplasms of the neuraxis (CAPNON) are very rare heavily calcified discrete intraparenchymal or extra-axial lesions that can occur anywhere along the neuraxis. 

Given the rarity of these lesions, detailed epidemiological data is not available. 

They usually asymptomatic and found incidentally but sometimes they can present with a seizure. 

CAPNONs are usually solitary extra-axial masses 3,4. An understanding of aetiology remains elusive with reactive, metaplastic and even neoplastic processes having been proposed 3.

They demonstrate extensive calcifications and a nodular chondromyxoid matrix with an amorphous quality and fibrovascular stroma. The spindle and epithelioid cells surrounding the matrix showed positive staining with antibodies against epithelial membrane antigen (EMA) 1-3. They are S100 and GFAP negative 3

Although the typical histopathologic features can be observed in most cases, some may be unusual and may be confused with calcified meningioma or tumoral calcinosis.

Can be seen a heavily calcified well-defined leptomeningeal or parenchymal mass.

Typical signal characteristics are those of calcium:

  • T1: iso to hypointense
  • T2: low signal on FLAIR and T2
  • T1 C+ (Gd): varies from none to moderate enhancement
  • T2*: mild blooming 

If resection is required then it is usually curative. Morbidity relates to operative complications and damage to structures adjacent to the mass 3,4

CAPNON should be considered in the imaging differential diagnosis of a heavily calcified lesion in neuroaxis and the differential will depend on the location. It is worth considering this entity to avoid aggressive surgical intervention in a lesion that is difficult to resect, as the natural history of CAPNON is generally indolent. 

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Article information

rID: 36495
Synonyms or Alternate Spellings:
  • Fibro-osseous lesions of the neuraxis
  • CAPNON
  • Calcifying pseudoneoplasms of the neuraxis

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