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.

A 41-year-old woman presented with refractory low back pain for the last 6 months. Neurologic examination was normal. Blood tests showed high erythrocyte sedimentation rate. A spine MRI (figure 1) disclosed involvement of the T12 vertebral body. There was hyperintense signal in T2-weighted sequence and multiple linear hypointense areas with cortical and radiated pattern resembling the brain parenchyma (the "mini brain" sign) (figure 2). Biopsy confirmed solitary plasmacytoma. Mini brain sign represents cortical thickening and is most likely caused by lytic lesions.1 The thickened struts resemble sulci in the brain, leading to a small brain appearance. 2,3 A "spoke-wheel" pattern has also been described. Mini brain sign is considered highly specific for solitary plasmacytoma.

No abstract