Final Diagnosis --Calcifying Pseudoneoplasm of the Neuraxis (CAPNON)


FINAL DIAGNOSIS

Calcifying pseudoneoplasm of the neuraxis (CAPNON), located in the cerebellopontine angle. It is a rare, uncommon and pathogenetic unexplained lesion. In the literature it is also described as "fibro-osseous lesion", "cerebral calculi" or "brain stone".

DISCUSSION

Calcifying pseudoneoplasms of the brain are rarely reported. Since the first reported case of a "Calculi within the brain" by Miller in 1929 [1] less than 100 clinical cases have been described in the literature. These lesions are often located intracranially but may also be observed in the spinal cord. The age of patients with this diagnosis ranges from 6 to 83 years, with a mean age of 46 years [2]. The histopathological background is not yet understood, but concerning the reported cases these lesions seems to be usually benign. It is discussed that they develop as a reactive response on unspecific stimulating factors rather than a neoplastic process [3, 4].

Typical differential diagnosis of preoperative imaging, depending on location, is meningioma, chordoma or chondrosarcoma as well as vestibular schwannoma. The typical T1 and T2 hypointensity of calcifying pseudoneoplasm [5] would be unusual for the described entities, except meningioma. Further important differential considerations for calcified lesions should contain tumors like gangliogliomas, oligodendrogliomas, vascular malformations and infections such as tuberculosis [3, 5]. Microscopically differential diagnosis include several reactive lesions such as granulomatosis, chondroid chordoma, chondroma /-sarcoma, metaplastic meningioma or other calcified primary parenchymal central nervous system tumors [6]. Calcifying pseudoneoplasms present classic histopathological characteristics containing calcification, osseus metaplasia, chondromyxoid matrix, fibrous stroma, spindle or epithelioid cells and also foreign-body reaction with giant cells. The characteristics are varying a lot, not all features must be present. The current immunohistochemical findings could not contribute to determine the etiology of the lesion. In reported cases the staining with GFAP and S-100 was negative. EMA was positive in a part of epithelioid cell elements but can also be negative as reported in other cases.

Concluding calcifying pseudoneoplasm is a rare differential diagnosis for calcifying tumors of the neuraxis. Although complete surgical resection is recommended even an incomplete resection as in the presented case bears a favorable prognosis. Therefore, a function preserving less aggressive surgical approach is justified.

REFERENCES

  1. Miller EA (1922) Calculi within the brain. A report of a case of intracranial calcification with successful operation and recovery. Surg Gynecol Obstet. 34:786-789.
  2. Nonaka Y, Aliabadi HR, Friedman AH, Odere FG, Fukushima T (2012) Calcifying pseudoneoplasms of the skull base presenting with cranial neuropathies: case report and literature review. J Neurol Surg reports. 73(1):41-47.
  3. Bertoni F, Unni KK, Dahlin DC, Beabout JW, Onofrio BM (1990) Calcifying pseudoneoplasms of the neural axis. J Neurosurg. 72(1):42-48.
  4. Qian J, Rubio A, Powers JM, et al. (1999) Fibro-osseous lesions of the central nervous system: report of four cases and literature review. Am J Surg Pathol. 23(10):1270-1275.
  5. Aiken AH, Akgun H, Tihan T, Barbaro N, Glastonbury C (2009) Calcifying pseudoneoplasms of the neuraxis: CT, MR imaging, and histologic features. AJNR Am J Neuroradiol. 30(6):1256-1260.
  6. Rodriguez FJ, Scheithauer BW, Fourney DR, Robinson CA (2008) Ependymoma and intraparenchymal calcifying pseudoneoplasm of the neural axis: incidental collision or unique reactive phenomenon? Acta Neuropathol. 115(3):363-366.
  7. Alshareef M, Vargas J, Welsh CT, Kalhorn SP (2016) Calcifying Pseudoneoplasm of the Cervicomedullary Junction: Case Report and Review of Literature. World Neurosurg 85(1):364.

Contributed by Susann Hetze, MD, Johannes van de Nes, MD, Sophia Goerike, MD, Sarah Teuber-Hanselman, MD, Ulrich Sure, MD, Neriman Oezkan




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