Calcifying Pseudoneoplasm of the Neuraxis: A Case Illustrating Natural History over 17 Years of Radiologic Surveillance

Spinal calcifying pseudoneoplasm of the neuraxis (CAPNON) associated with facet joint pathologies: CAPNON diagnostic and pathogenic insights

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumor-like fibro-osseous lesion that can develop anywhere in the neuraxis. Approximately a half of reported CAPNONs developed in the spinal region, mostly close to the facet joint (FJ). The diagnosis of spinal CAPNONs is challenging given the existence of mimics and associated pathologies including calcific degeneration of the FJ ligaments (DFJL) and synovial cysts (SCs). The pathogenesis of CAPNON remains elusive, although there have been a few hypotheses including degenerative, reactive, proliferative and immune-mediated processes. Our present study examined clinical, radiological and pathological features of 12 spinal CAPNONs in comparison to 9 DFJL foci, and diagnostic and pathogenic relationship between CAPNONs and FJ pathologies. On imaging, CAPNONs were all tumor-like and typically bigger than DFJL foci. All CAPNONs showed pathologically diagnostic features including characteristic cores, consistently identifiable core-surrounding/peripheral palisading of macrophages and other cells including multinucleated giant cells, variable infiltration of CD8+ T-cells, and multifocal immunopositivity of neurofilament light chain (NF-L). These features were absent or limited in the DFJL foci with statistically significant differences from CAPNONs, except calcifications. Spinal CAPNONs co-existed with DFJL foci in all cases; some had transitional foci with overlapping focal CAPNON and DFJL-like features. These findings, along with our previously reported relationship between CAPNONs and SCs, suggest that spinal CAPNONs may occur in association with or in transition from calcifying/calcified degenerative lesions of FJ ligaments and/or SCs when a reactive proliferative process is complemented by other pathogenic changes such as immune-mediated pathology and NF-L deposition/expression.

Calcifying Pseudoneoplasm of the Neuraxis: An Institutional Series of Ten Cases and Review of the Literature to Date

BACKGROUND

Calcified pseudoneoplasms of the neuraxis (CAPNONs) are rare, fibro-osseous lesions with an unknown cause that may present anywhere along the neuroaxis. Little is known about how intracranial CAPNONs present and about patients' long-term outcomes.

METHODS

A retrospective institutional review of intracranial pathology-confirmed CAPNONs was performed. Presenting clinical features, management, and clinical outcomes are highlighted. A literature review of intracranial CAPNON lesions was also performed to build on our series.

RESULTS

Ten patients were identified who met the inclusion criteria. Most patients presented with headaches (n = 6; 60%), seizures (n = 5; 50.0%), and neck and facial pain (n = 3; 30.0%). Most lesions were supratentorial (n = 7; 70.0%), with 3 infratentorial origins. Surgical resection was the most common initial management undertaken (n = 7; 70.0%). No new permanent postoperative neurologic deficits were identified. The median clinical and/or radiographic follow-up for all patients was 6.8 years (range, 0.7-23.3 years), with no recurrence of disease for 5 patients who underwent gross total resection. Four of 5 patients with residual or nonresectable lesions showed no interval growth on radiographic follow-up; 1 patient showed progression and worsening of presenting symptoms 2 months after resection. Resection substantially improved seizures and headaches in patients presenting with these symptoms (80% and 83.3%, respectively).

CONCLUSIONS

Intracranial CAPNONs may present with a wide variety of symptoms characteristic of the site of origin. The outcomes of these symptoms regarding survival and disease control are generally favorable, although resection does not always yield complete resolution of presenting deficits in certain patients, particularly those presenting with headaches or neck/facial pain.

Posterior Fossa Calcifying Pseudoneoplasm of the Neuraxis (CAPNON): Presentation of Three Surgical Cases

BACKGROUND

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is an extremely rare entity with fewer than 150 cases reported in the literature and mostly with a supratentorial or spinal location. Posterior fossa CAPNON has been reported scarcely, and association with perilesional edema is a topic not yet approached which might play a significant role in treatment decision and clinical progression. Our objective is to report, to our knowledge, the first series of 3 posterior fossa CAPNON surgically treated in a single institution and assess features that help provide a systematic approach to diagnosis and timely treatment.

METHODS

This was a monocentric, retrospective study of surgical patients diagnosed with a posterior fossa CAPNON in the last 5 years. A thorough bibliographic research was conducted.

RESULTS

Three patients were included. Locations involved IV ventricle, right cerebellopontine angle with extension to foramen magnum, and cerebellar vermis. Two of them presented with symptoms linked to acute hydrocephalus, and the other one presented with progressive cranial nerve palsy and brainstem compression signs. The 3 of them showed radiological signs of perilesional edema on their preoperative magnetic resonance imaging. Gross total resection was accomplished in one case, with near and subtotal resections in the others. There were no complications. The outcome was favorable in all cases.

CONCLUSIONS

It is essential to contemplate this infrequent diagnosis in cases of calcified lesions involving the posterior fossa. When symptoms manifest, surgery should be considered. Perilesional edema could be associated with symptomatic progression and hence a sign suggesting the need for surgical treatment.

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

Calcifying pseudoneoplasms of the neuraxis (CAPNONs) are uncommon benign lesions that are rarely diagnosed radiographically. We report an unusual case of a left middle cerebellar peduncle CAPNON with vasogenic edema and a perilesional cyst. The patient was a 36-year-old woman with a 20-year history of left-sided hearing loss that had recently progressed. Computed tomography and magnetic resonance imaging showed a heterogenous calcified lesion with vasogenic edema and a perilesional cyst in the left middle cerebellar peduncle. Although it is a rare radiographic feature of CAPNON, vasogenic edema should be included as a possible feature of this uncommon tumefactive lesion.

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

Calcifying pseudoneoplasms of the neuraxis (CAPNON) are very rare intracranial lesions with less than 50 cases reported in literature. These are non-neoplastic in etiology and despite having unique imaging characteristics, are often misdiagnosed as a neoplastic condition like meningioma, chordoma and gliomas. These do not have any predilection for any age, gender or intracranial location and can be seen in a wide range of age groups. Despite having an imaging overlap with neoplastic conditions, CAPNONs have classic histopathologic findings including chondromyxoid matrix, palisading spindle cells and calcific or ossific metaplasia. As more cases are being described in literature the imaging features are also being better defined. We discuss the clinical, imaging and histopathological findings of 2 cases of CAPNON mimicking posterior fossa meningioma and glial neoplasm.

Calcifying pseudoneoplasm of the neuraxis within the sellar region: illustrative case

BACKGROUND

There are numerous atypical lesions of the sellar and suprasellar region that are often mistaken for pituitary adenomas. It is important to consider rare mimics of more common pathologies in this region.

OBSERVATIONS

The authors detail the case of a 37-year-old woman with hypopituitarism who was found to have an atypical sellar mass with slow growth on interval imaging. The lesion was debulked via a microscopic endonasal transsphenoidal approach and found to be a calcifying pseudoneoplasm of the neuraxis (CAPNON).

LESSONS

CAPNON is a rare disease entity that may affect the sellar region. CAPNON should be on the differential diagnosis for sellar masses that are associated with T1 and T2 hypointensity on magnetic resonance imaging with minimal enhancement. Although CAPNON is not at risk for malignant progression, these benign lesions can continue to grow after a subtotal resection and require follow-up.

Calcifying Pseudoneoplasm of the Neuraxis in the Posterior Fossa: A Case Report and Literature Review

Calcifying pseudoneoplasm of the neuraxis are rare fibro-osseous lesions that can occur throughout the central nervous system. This paper reports one case of this lesion within the posterior fossa and contains a literature review of all cases documented within the posterior fossa to date. A 53-year-old female patient with a history of epiphora, facial irritation, and headaches was found to have a mass centered in the posterior fossa. The patient underwent surgical resection for removal of the mass. Upon review by pathology, the final diagnosis was consistent with calcifying pseudoneoplasm of the neuraxis.

Calcifying pseudoneoplasms of the neuraxis (CAPNON). A case report

Calcifying pseudoneoplasms of the neuraxis (CAPNON) are rare, slow-growing, benign lesions occurring throughout the neuroaxis that are frequently misdiagnosed and overlooked by clinicians. Here, we report a case of a 56-year-old woman who presented with a history of recurrent headache for the previous six years. Magnetic resonance imaging (MRI) revealed a 2.3-cm-sized solid mass in the right frontal lobe that was surrounded by marked edematous areas. The lesion demonstrated dense calcification and avid enhancement. The lesion was initially diagnosed as oligodendroglioma, and then found to be CAPNON based on histopathology of a surgically resected tissue. Genetic analysis revealed a nonsense mutation in the CUL4B gene. The patient's condition appeared to reflect a reactive, rather than neoplastic, process. Clinicians should be prepared to detect such pseudotumors histopathologically in order to avoid unnecessary differential tests of neoplastic or infectious diseases, as well as potentially harmful therapies.

Skull Base Calcifying Pseudoneoplasms of the Neuraxis: Two Case Reports and a Systematic Review of the Literature

BACKGROUND

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumefactive lesion. CAPNONs can mimic calcified meningiomas at the skull base.

METHODS

Here, we report two cases of CAPNON and present a systematic review of the literature on skull base CAPNONs, to compare CAPNONs with calcified meningiomas.

RESULTS

Case 1: A 57-year-old man presented with right-sided lower cranial neuropathies and gait ataxia. He underwent a subtotal resection of a right cerebellopontine angle lesion, with significant improvement of his gait ataxia. However, his cranial neuropathies persisted. Pathological examination of the lesion was diagnostic of CAPNON, with the entrapped nerve fibers identified at the periphery of the lesion, correlating with the patient's cranial neuropathy. Case 2: A 70-year-old man presented with progressive headache, gait difficulty, and cognitive impairment. He underwent a frontotemporal craniotomy for a near-total resection of his right basal frontal CAPNON. He remained neurologically stable 7 years after the initial resection without evidence of disease recurrence. We analyzed 24 reported CAPNONs at the skull base in our systematic review of the literature. Cranial neuropathies were present in 11 (45.8%) patients. Outcomes regarding cranial neuropathies were documented in six patients: two had sacrifice of the nerve function with surgical approaches and four had persistent cranial neuropathies.

CONCLUSION

While CAPNON can radiologically and grossly mimic calcified meningiomas, they are two distinctly different pathologies. CAPNONs located at the skull base are commonly associated with cranial neuropathies, which may be difficult to reverse despite surgical intervention.

Giant calcified pseudoplasm of the nerve axis of the temporal lobe: a case report and review of the literature

Calcifying pseudoneoplasms of the neuraxis (CAPNONs) are rare and can occur along the neural axis. The pathogenesis of these masses is still unknown, and they are diagnosed by histopathological analysis. We report the largest CAPNON in the temporal lobe reported to date and a review of the literature on all previously reported CAPNON cases located in the temporal lobe. According to the literature review, prior to 2020, the largest CAPNON in the temporal lobe that had ever been reported measured 30 × 30 × 20 mm (Mohapatra et al.). However, we report a larger temporal lobe CAPNON (45 × 35 × 35 mm) in a female patient admitted to our hospital. In addition, among 22 patients with CAPNONs aged from 6 to 62 years, 45.5% were female and 54.5% were male. A total of 72.8% of patients presented with seizures, 9.1% had pituitary dysfunction and 9.1% did not have symptoms. Of the cases in the patients with seizures, 83.2% were completely surgically resected, 5.6% were partially surgically resected, and one was treated medically; one patient refused treatment. Except for one patient who had multiple lesions, all patients who underwent surgery exhibited improved or the disappearance of symptoms of epilepsy. The patient in whom epilepsy resolved had undergone total resection. CAPNON is a rare benign lesion that occurs throughout the nervous system, and the pathogenesis remains unclear. Although the hardness of these lesions vary, surgery is still the preferred treatment and yields good results, and total resection is recommended for patients with epilepsy in the temporal lobe.

Calcifying Pseudoneoplasm of the Neuraxis: From Pathogenesis to Diagnostic and Therapeutic Considerations

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumefactive lesion that can develop anywhere within the neuraxis. The incidence is likely underreported, given its nonspecific imaging features and because CAPNON has often been overwhelmed by the presence of comorbid disease. CAPNON is typically diagnosed by the histopathological examination findings. However, the histopathological diagnosis is often challenging owing to the existence of similar calcifying pathological entities. Although the pathogenesis of CAPNON has remained elusive, emerging evidence supports a reactive proliferative and immune-mediated process involving the aggregation of neurofilament light chain protein and the infiltration of immune cells. The management of CAPNON is largely dependent on the symptoms, which are mainly related to the location and associated mass effects. Maximal surgical resection will result in excellent patient outcomes with rare recurrence, especially in patients presenting with epilepsy. The discovery of neurofilament light chain protein within CAPNON suggests that neurofilament might be implicated in the pathogenesis of CAPNON, serve as an immunohistochemical marker to improve the diagnostic accuracy of CAPNON, and hold therapeutic potential for the treatment of CAPNON.

Immunohistochemical Markers in the Diagnosis of Calcifying Pseudoneoplasm of the Neuraxis

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.

Collision Lesions of Calcifying Pseudoneoplasm of the Neuraxis and Rheumatoid Nodules: A Case Report With New Pathogenic Insights

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare tumor-like lesion with unclear pathogenesis. Collision lesions of CAPNONs with neoplasms are occasionally reported. In this article, we report the first case of collision lesions between CAPNON and rheumatoid nodules (RNs) in a patient with systemic lupus erythematosus. The patient was a 51-year-old female who presented with lower back pain and subsequently a lower back mass over 2 years. Spinal magnetic resonance imaging demonstrated a heterogeneous, partially calcified mass centered in the L3-4 paravertebral regions. A biopsy of the mass was diagnostic of CAPNON. As the mass grew over the following 5 months, it was resected en bloc. Its pathological examination revealed collision lesions of RNs at different histopathological stages and CAPNON lesions, and transitional lesions exhibiting combined RN and CAPNON features, with immune cell infiltrates. Our findings provide new evidence for an immune-mediated reactive process and insights into the pathogenies of CAPNON.

New insights into calcifying pseudoneoplasm of the neuraxis (CAPNON): a 20-year radiological-pathological study of 37 cases

AIMS

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare entity that can occur anywhere within the central nervous system. Histologically, CAPNON has been characterised as a benign, calcified, fibro-osseous lesion with a characteristic chondromyxoid fibrillary matrix with dense calcification and varying degrees of spindle, epithelioid, fibrous, meningothelial and giant cells. The underlying aetiology of CAPNON is controversial and incompletely understood. The aim of this study was to perform a comprehensive radiological and histological review to further characterise this entity.

METHODS AND RESULTS

In this article, we review our institutional 20-year experience including 37 cases of CAPNON with detailed pathological analysis, evaluation of concurrent lesions, correlation with radiological imaging, and critical review of the literature. The classic histological finding of chondromyxoid matrix was present in one-third of cases. Underlying or dual pathologies were frequent, and included diverse underlying conditions. Radiologically, dense calcification and dural attachment were the most common features. Enhancement was often low, but was more prominent in the setting of inflammatory changes, aggressive growth, and dual pathology.

CONCLUSION

Our results suggest that CAPNON represents a spectrum of reactive processes that can arise in association with diverse underlying pathologies, including inflammatory, degenerative, vascular and neoplastic lesions.

Calcifying pseudoneoplasm of the neuroaxis presenting with refractory seizures: Case report and literature review

Calcifying pseudoneoplasms of the neuraxis (CAPNON) are rare benign lesions that can arise anywhere within the central nervous system. The etiology of these lesions remains unknown and diagnosis is made on pathohistological analysis. We present the case of a 35-year-old male patient with a history of epilepsy since childhood who was evaluated for refractory seizures. MRI revealed a small lesion in the left-posterior temporal lobe suspected to be a cavernoma. A gross total resection of the lesion was achieved via a left temporal craniotomy and pathological analysis revealed CAPNON. At 6 months follow-up, the patient remained neurologically intact and his seizures had ceased.

Incidental multifocal calcifying pseudoneoplasm of the neuraxis: case report and literature review

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is thought to be a rare tumefactive lesion with unknown pathogenesis. Its prevalence is questionable with few previously reported cases of incidental CAPNON, and likely underdiagnosis. We report a unique case of incidental multifocal CAPNON. A 64-year-old female was admitted with loss of consciousness due to a ruptured right middle cerebral artery aneurysm with subarachnoid and intraventricular hemorrhage. She has a craniotomy and clipping. At time of operation, numerous small dural-based nodules were found, and one was excised for biopsy and was diagnosed as CAPNON. Retrospective review of her CT images identified nodules that were all ipsilateral to the ruptured aneurysm. A literature review revealed that incidental and/or multifocal CAPNONs are rare but likely underreported. Our case suggests a reactive process in the pathogenesis of CAPNON.

Surgically treated intracranial supratentorial calcifying pseudoneoplasms of the neuraxis (CAPNON) with drug-resistant left temporal lobe epilepsy: A case report and review of the literature

Calcifying pseudoneoplasms of the neuraxis (CAPNON) are rare pathological lesions that can present anywhere in the central nervous system. Symptoms vary depending on the location, though they often include seizures, especially in intracranial and supratentorial lesions. A case of intracranial supratentorial CAPNON presenting with drug-resistant left temporal lobe epilepsy is reported. The patient had a history of drug-resistant focal seizures for over 36 years. The lesion was located in the left mesial temporal lobe, but hippocampal sclerosis and hippocampal invasion were not apparent. The lesion was removed without hippocampectomy, and the patient has been seizure-free for one year.