Ancient olfactory schwannoma - case report and literature review

Abstract

ABSTRACTsignal intensity on T2-weighted images. The signal intensity on T2-weighted images may be either homogeneously hyperintense or it can show a characteristic high signal intensity in the periphery and low signal intensity in the central region of the lesion. This MR imaging finding corresponds with pathologic findings to fibrous tissue (with high collagen content) centrally and more myxoid tissue peripherally (20).Histopathologically, it consists of compact hypercellular Antoni A areas and myxoid hypocellular Antoni B areas. Cells are narrow, elongated and wavy with tapered ends interspersed with collagen fibers -spindle cells. Nuclear palisading around fibrillary processes (Verocay bodies) are often seen in cellular areas. Large irregularly spaced vessels, usually with thickened hyalinized walls and thrombi, are most prominent in Antoni B areas. Tumor cells have ill-defined cytoplasm, dense chromatin. It often displays degenerative nuclear atypia, but █ INTRODUCTION I ntracranial schwannomas are benign tumors that arise from Schwann cells. Since it is well known that optic and olfactory nerves do not have a Schwann cell sheath, schwannoma should not develop from these nerves (17).Schwannomas account for 8 -10 % of all intracranial tumors and occur mostly in patients between 20 and 50 years of age. Patients affected by schwannomas may be asymptomatic or present with various symptoms depending on the location, size and nerve of origin, and may include motor and sensory dysfunction, intracranial hypertension, headache and seizures (20).These tumors present on Magnetic Resonance Imaging (MRI) as well-circumscribed, encapsulated masses, low-to intermediate signal intensity on T1-weighted images and high Intracranial schwannomas are benign tumors that arise from Schwann cells. Since it is well known that optic and olfactory nerves do not have a Schwann cell sheath, schwannoma should not develop from these nerves.We report a very unusual case of a 73-year-old female who presented with generalized seizures and had radiological features of an intracranial aneurysm. Additional imaging showed an extracerebral mass 2.5 x 2.0 cm in size, which most likely corresponded to a meningioma. It was resected in total. Subsequent histological analysis revealed that the tumor was in fact ancient schwannoma WHO grade I.Only about 41 case of olfactory schwannoma have been reported in the literature. Olfactory groove schwannomas are extremely rare tumors, occurring less frequently than any other intracranial nerve schwannoma. As in this case, the schwannoma should be included in the differential diagnosis of the anterior cranial fossa tumor. Further research on the pathogenesis and the origin of olfactory groove schwannoma is needed.

Olfactory Groove Schwannoma or Olfactory Ensheathing cell Tumor?

“…When considering the differential diagnosis for OGSs, an olfactory groove meningioma should be the first choice 14–16 . The differential diagnosis also included glioma, neuroblastoma, metastatic, and abcess 5,17,18 . There have been some literature that summarized the differential diagnosis of OGSs 14,15 .…”

Olfactory Nerve Schwannoma: A Case Report and Review of the Literature

“…The origin of this entity is still debatable, since the fact that olfactory nerve lacks Schwann cells and has only oligodendrocytes. 5 Existing theories suggest that these tumors arise from aberrant Schwann cells in the central nervous system (CNS), 6 another theory suggests its transformation from mesenchymal pial cells or migration of neural crest cells present inside the CNS, 7 both these theories may explain the origin of intraparenchymal schwannomas. 2 Some basic science publications came to findings that olfactory nerve has schwann cells, which arise from precursor cells, which are present in the olfactory epithelium, and this makes the fact about presence of schwann cells, or not in the olfactory nerve unsettled yet.…”

Olfactory Groove Schwannoma—A Case Report and Literature Review

“…6 Aware that optic and olfactory nerves, as part of the central nervous system (CNS), 7 do not have a Schwann cell sheath, and that intracranial schwannomas unrelated to cranial nerve occur mainly in the midline of the anterior cranial fossa, there is a divergence concerning the origin of OGSs and whether they are primarily intra or extra-axial lesions. 1,3,6 Despite several hypothesis concerning their probable origin, the true original site of OGSs remains controversial. 3,5 Developmental theories suggest an intraparenchymal origin, 1 either by transformation of a mesenchymal pial cell into ectodermal Schwann cells or by the migration of neural crest cells within the CNS.…”

“…1,3,6 Despite several hypothesis concerning their probable origin, the true original site of OGSs remains controversial. 3,5 Developmental theories suggest an intraparenchymal origin, 1 either by transformation of a mesenchymal pial cell into ectodermal Schwann cells or by the migration of neural crest cells within the CNS. 6 Still, there is a theory suggesting the origin of Schwann cells from multipotent mesenchymal cells after an injury.…”

“…4 The majority of the cases are located in the vestibular portion of the 8th cranial nerve, and less commonly on the 5th, the 9th, the 10th and the 12th cranial nerves. 1,3 Extremely rare and with an enigmatic origin, schwannomas are found in the anterior cranial fossa, specially in the olfactory groove. 2 We report the case of an olfactory groove schwannoma (OGS) along with a brief literature review of the pathogenesis and origin of the schwanommas.…”