Abstract
Background: Calcifying pseudoneoplasm of the neuroaxis (CAPNON) is a very rare benign lesion that can be located anywhere in the nervous system, with only 59 intracranial cases described. The general lack of knowledge about this lesion hinders its preoperative diagnosis. Despite the consistent image findings, the final diagnosis is only established based on anatomopathological and immunohistochemical studies. The lesion is more commonly positive for epithelial membrane antigen (EMA) and vimentin, and negative for glial fibrillary acidic protein (GFAP) and S-100, suggesting a leptomeningeal origin. The opposite, however, may also occur, although very rarely (just two cases positive for GFAP and negative for EMA and vimentin reported this far). The treatment consists of total resection of the lesion, which yields a good prognosis. Case Presentation: We report the case of a 23-year-old female who presented with disperceptive focal seizures, sometimes evolving to bilateral tonic-clonic seizures, starting at age 9. She had a nodular calcified lesion in the left precuneus and inferior parietal lobe. The lesion was completely resected, and the immunohistochemical study revealed positivity for EMA, vimentin, GFAP, and S-100. No case hitherto published was positive for all four markers. This atypical immunohistochemical profile of the CAPNON may suggest a dual origin of this lesion, both parenchymal and leptomeningeal. Conclusion: The general lack of knowledge of CAPNON makes this lesion underdiagnosed. Therefore, in the face of a calcified lesion in the nervous system, one should consider the possibility of a CAPNON among the differential diagnoses. The immunohistochemistry is undoubtedly an important tool, but the anatomopathological study, associated with image findings, remain the gold standard for the diagnosis of CAPNON.
Highlights
Calcifying pseudoneoplasm of the neuroaxis (CAPNON) is a very rare benign lesion that can be located anywhere in the nervous system, with only 59 intracranial cases described
Case Presentation: We report the case of a 23-year-old female who presented with disperceptive focal seizures, sometimes evolving to bilateral tonic-clonic seizures, starting at age 9
In the face of a calcified lesion in the nervous system, one should consider the possibility of a CAPNON among the differential diagnoses
Summary
The nosological entity called calcifying pseudoneoplasm of the neuroaxis (CAPNON) was first described by Rhodes and Davis more than 40 years ago, but its etiopathogenesis remains still unclear [1]. With just 59 intracranial cases described, the disease presents nonspecific clinical manifestations, but a suggestive imaging aspect, which helps its diagnosis [2, 3] This can be located in any region of the nervous system, determining the appearance of seizures, cranial nerves deficits, radiculopathies, and refractory headaches, among other findings. The lesion was well circumscribed, not encapsulated, and composed predominantly of spindle cells, with indistinct cytoplasm It presented a delicate and fibrillar stroma with a prominent presence of calcified bodies, similar to psammomas, uniformly arranged (Figure 3). On CD34, no vascular anomalies were observed, and the reticulin stain revealed intact and parallel fibers Based on these findings and on those from the imaging studies, the diagnosis of CAPNON was established. She remains seizure-free since surgery and the anticonvulsant therapy (carbamazepine) was progressively discontinued
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