Immunohistochemical Markers in the Diagnosis of Calcifying Pseudoneoplasm of the Neuraxis

Abstract

Background: Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumor-like lesion with unknown pathogenesis. It is likely under-reported due to diagnostic challenges including the nonspecific radiographic features, lack of diagnostic markers, and often asymptomatic nature of the lesions. Methods: We performed detailed examination of 11 CAPNON specimens diagnosed by histopathology, with the help of electron microscopy and immunohistochemistry. Results: Electron microscopy revealed the presence of fibrillary materials consistent with neurofilaments. In addition to some entrapped axons at the periphery of CAPNONs, we discovered that all specimens stained positive for neurofilament-light (NF-L) within the granular amorphous cores, but not neurofilament-phosphorylated (NF-p). CAPNONs also showed variable infiltration of CD8+ T-cells and a decreased ratio of CD4/CD8+ T-cells, suggesting an immune-mediated process in the pathogenesis of CAPNON. Conclusion: NF-L and CD4/CD8 immunostains may serve as diagnostic markers for CAPNON and shed light on its pathogenesis.

Calcifying pseudoneoplasms of the neuraxis (CAPNON): The great tumor mimicker

“…They are slow-growing benign lesions presumably attributable to a reactive proliferative process induced by various trigger factors, such as infection, inflammation and injury, and may be possibly associated with inflammatory, degenerative, vascular and neoplastic diseases [2] , [3] , [4] . However, its underlying etiology is still non completely defined and other explanations have been proposed too, including neoplastic process [5] , immune-mediated process [6] , tissue calcinosis [7] , and less likely, metaplastic transformation [8] . Total surgical resection is considered the gold standard of treatment and no additional chemotherapy or radiotherapy is needed [9] , even if some cases of recurrence or local progression after surgery have been described in literature [10] , [11] , [12] .…”

“…2 In these cases, differential diagnosis may include infectious granulomatous diseases, foreign body reaction and neoplasms such as chordomas, chondro-blastomas, chondrosarcomas and metaplastic meningioma [ 4 , 24 ]. As regards immunohistochemistry, the peripherical palisading cells are positive for epithelial membranous antigen (EMA) and vimentin and are negative for glial fibrillary acidic protein, smooth muscle actin, and S-100 protein, even if the latter has been shown to be positive in some cases [ 6 , 24 ]. Among these, EMA may represent an immunohistochemical marker helpful to distinguish CAPNONs from calcified psammomatous and metaplastic meningiomas.…”

Calcifying Pseudoneoplasm of the Neuraxis Involving the Posterior Skull Base: A Case Report and Literature Review

“…12 Recently, an immunohistochemistry study on 11 CAPNON cases showed that the granular amorphous cores of the CAPNON were positive for neurofilamentlight chain, a cytoplasmic protein expressed in the axons, and there was also evidence of CD8+ cytotoxic T-cells infiltration with a decreased ratio of CD4/CD8 T-cells in the lesions. 30 Based on these findings, they hypothesized that the pathogenesis of CAPNON might be an immunemediated process. 30 Clinical presentation of CAPNON is not specific and depends on its anatomic location, size, local mass effect, and irritation of adjacent tissues.…”

“…30 Based on these findings, they hypothesized that the pathogenesis of CAPNON might be an immunemediated process. 30 Clinical presentation of CAPNON is not specific and depends on its anatomic location, size, local mass effect, and irritation of adjacent tissues. Seizures and headache are the most common symptoms of intracranial CAPNON, and pain is most often seen in spinal CAPNON.…”

Calcifying Pseudoneoplasm of the Neuraxis Presenting with Vasogenic Edema and a Perilesional Cyst

“… 1 4 The clinical presentations of these lesions vary, depending on the location, size, and associated mass effect. 1 5 6 7 8 Although CAPNONs are typically definitively diagnosed histopathologically postresection, 9 radiographic imaging is an important part of the workup. Vasogenic edema is a rare feature on magnetic resonance imaging (MRI), and concurrent perilesional cysts have not been reported in the literature.…”