Glial fibrillary acidic protein immunopositive neuroglial tissues with or without ependyma-lined canal in spinal lipoma of filar type: Relationship with retained medullary cord.

BACKGROUND

Retained medullary cord (RMC) and filar lipomas are believed to originate from secondary neurulation failure; filar lipomas are reported to histopathologically contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissue with ependyma-lined central canal (NGT w/E-LC) as a remnant of the medullary cord, which is a characteristic histopathology of RMC. With the addition of glial fibrillary acidic protein (GFAP) immunostaining, we reported the presence of GFAP-positive NGT without E-LCs (NGT w/o E-LCs) in RMC and filar lipomas, and we believe that both have the same embryopathological significance.

METHODS

We examined the frequency of GFAP-positive NGT, with or without E-LC, in 91 patients with filar lipoma.

RESULTS

Eight patients (8.8%) had NGT w/E-LC, 25 patients (27.5%) had NGT w/o E-LC, and 18 patients (19.8%) had tiny NGT w/o E-LC that could only be identified by GFAP immunostaining. Combining these subgroups, 56% of the patients (n = 51) with filar lipoma had GFAP immunopositive NGT.

CONCLUSION

The fact that more than half of filar lipomas have NGT provides further evidence that filar lipoma and RMC can be considered consequences of a continuum of regression failure that occurs during late secondary neurulation.