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Year : 2009  |  Volume : 57  |  Issue : 1  |  Page : 76-78

Olfactory ensheathing cell tumor

1 Department of Neurosurgery, Apollo Hospitals, Jubilee Hills, Hyderabad - 500 033, Andhra Pradesh, India
2 Department of Pathology, Apollo Hospitals, Jubilee Hills, Hyderabad - 500 033, Andhra Pradesh, India

Date of Acceptance05-Feb-2009

Correspondence Address:
Rahul Lath
Department of Neurosurgery, Apollo Hospitals, Jubilee Hills, Hyderabad - 500 033, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.48811

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 » Abstract 

Olfactory ensheathing cells (OECs) are found in the olfactory bulb and olfactory nasal mucosa. They resemble Schwann cells on light and electron microscopy, however, immunohistochemical staining can distinguish between the two. There are less than 30 cases of olfactory groove schwannomas reported in the literature while there is only one reported case of OEC tumor. We report an OEC tumor in a 42-year-old male and discuss the pathology and origin of this rare tumor.

Keywords: Brain tumor, olfactory ensheathing cell tumor, olfactory schwannoma

How to cite this article:
Ippili K, Ratnam BG, Gowrishankar S, Ranjan A, Lath R. Olfactory ensheathing cell tumor. Neurol India 2009;57:76-8

How to cite this URL:
Ippili K, Ratnam BG, Gowrishankar S, Ranjan A, Lath R. Olfactory ensheathing cell tumor. Neurol India [serial online] 2009 [cited 2022 Jun 30];57:76-8. Available from: https://www.neurologyindia.com/text.asp?2009/57/1/76/48811

 » Introduction Top

Olfactory ensheathing cells (OECs) have the characteristics of both astrocytes and schwann cells. [1] They ensheathe olfactory axons and have the unique ability to regenerate and have been successfully applied in different experimental models aimed to repair damaged cord. [2] OECs are similar to Schwann cells in light and electron microscopic appearance, however, immunohistochemical staining can distinguish between the two. [3] Olfactory groove schwannomas are extremely rare, only 30 cases have been documented in the English literature, we could find only one reported case of OEC tumor. [3] We report a case of olfactory groove tumor showing features consistent with an OEC tumor.

 » Case Report Top

A 42-year-old man presented with history of multiple episodes of generalized tonic clonic seizures. There were no neurocutaneous markers. Olfaction was normal and there were no focal neurological deficits. Computerized tomography (CT) scan of the brain showed an extra-axial isodense mass in the left subfrontal region which enhanced homogenously with contrast. On magnetic resonance imaging (MRI) the lesion was isointense on T1-weighted images and mildly hyperintense on T2-weighted images and fluid-attenuated inversion recovery sequence [Figure 1]. He underwent a left frontal craniotomy and excision of the tumor. It was a partly suckable and fibrous tumor arising from the left olfactory bulb. Light microscopy showed spindle cells arranged in short fascicles, palisades and whorls. The cells were spindled out with curved vesicular nuclei and ill-defined cytoplasmic margins [Figure 2a]. On immunohistochemical staining the cells were strongly positive for S100 protein [Figure 2b] and negative for epithelial membrane antigen (EMA), glial fibrillary acidic protein (GFAP) and smooth muscle actin (SMA). However the tumor cells were negative for CD57 (Leu7). The immunohistochemical studies suggested that the cell of origin of the tumor was OEC rather than the Schwann cell. Patient is doing well at one-year follow-up and postoperative CT scan showed complete excision of the lesion.

 » Discussion Top

OECs share features of both Schwann cells of the peripheral nervous system (PNS) and astrocytes of the central nervous system (CNS). During development OECs emerge from the olfactory placode while Schwann cells from the neural crest, thus sharing a common peripheral origin. [1] Both cell types are known to express a number of different molecular markers in common, display a similar morphological phenotype in culture and respond to the same growth-promoting molecules. [1] Recent studies show that OECs have been successfully isolated from the human olfactory bulb and olfactory mucosa. [4] Studies have shown that OECs express smooth muscle protein alpha actin both in vitro and in vivo which provides evidence that these cells are quite different from Schwann cells. [5] These cells are similar to Schwann cells on light and electron microscopy. [3] On immunohistochemical staining Schwann cells are positive for S100 and Leu7 (CD57) while OECs are positive for S-100 and negative for Leu7 (CD57). [3] Both are negative for EMA differentiating them from meningiomas.

Olfactory groove and subfrontal schwannomas are rare tumors with lesser than 30 cases reported in the literature, of which six have been from India. [6],[7],[8],[9],[10],[11] The CNS does not possess Schwann cells and therefore the origin of this tumor has been debated. These tumors may arise from the olfactory bulb and nerve or an intracranial peripheral nerve closely associated with the olfactory nerve. [12] Occasionally, an intracranial schwannoma may arise at a site not related to a cranial nerve. The origin of these tumors could be from 1) hyperplasia of the Schwann cells localized within the perivascular nerve plexuses, 2) meningeal branch of the trigeminal nerve in the anterior cranial fossa, 3) anterior ethmoidal nerve around the cribriform plate, 4) hamartomatous lesion consisting of Schwann cells as a result of displaced neural crest cells and 5) reactive changes after injury whereby Schwann cells arise from multipotent mesenchymal cells after injury. [13]

Schwannomas at this location are preoperatively misdiagnosed as meningiomas, ethesio-neuroblastomas and dural-based metastases. [11],[14] The presence of bone scalloping and the absence of bone sclerosis and a dural tail may help in differentiating it from a meningioma. [14] A case of cystic olfactory groove schwannomas has also been reported. [8] A recent report has suggested that T2-weighted MRI sequence may help in distinguishing meningioma from schwannoma. [11] Presence of multiple foci of low signal intensities (related to microbleeds) in T2-weighted MRI may point towards a schwannoma.

Yasuda et al. , reported a patient with OEC tumor. [3] They used immunohistochemistry to differentiate it from a schwannoma. These authors have suggested that OECs are the origin of subfrontal /olfactory groove tumors rather than the Schwann cell as seen in our patient. Using this hypothesis, some of the previously reported olfactory groove schwannomas may have been OEC tumors. The use of tumor markers (S100 and CD57) as an adjunct to microscopy would help in differentiating these tumors. Surgical excision remains the mainstay of treatment and total excision is considered curative. Radiation therapy has been used for residual schwannomas at this location. [9]

 » References Top

1.Wewetzer K, Verdú E, Angelov DN, Navarro X. Olfactory ensheathing glia and Schwann cells: Two of a kind? Cell Tissue Res 2002;309:337-45.  Back to cited text no. 1    
2.Choi D, Law S, Raisman G, Li D. Olfactory ensheathing cells in the nasal mucosa of the rat and human. Br J Neurosurg 2008;22:301-2.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Yasuda M, Higuchi O, Takano S, Matsumura A. Olfactory ensheathing cell tumor: A case report. J Neurooncol 2006;76:111-3.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Miedzybrodzki R, Tabakow P, Fortuna W, Czapiga B, Jarmundowicz W. The olfactory bulb and olfactory mucosa obtained from human cadaver donors as a source of olfactory ensheathing cells. Glia 2006;54:557-65.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Jahed A, Rowland JW, McDonald T, Boyd JG, Doucette R, Kawaja MD. Olfactory ensheathing cells express smooth muscle alpha-actin in vitro and in vivo. J Comp Neurol 2007;503:209-23.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Husain M, Mishra UK, Newton G, Husain N. Isolated olfactory groove neurilemmoma. Surg Neurol 1992;37:115-7.  Back to cited text no. 6  [PUBMED]  
7.Praharaj SS, Vajramani GV, Santosh V, Shankar SK, Kolluri S. Solitary olfactory groove schwannoma: Case report with review of the literature. Clin Neurol Neurosurg 1999;101:26-8.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Shenoy SN, Raja A. Cystic olfactory groove schwannoma. Neurol India 2004;52:261-2.  Back to cited text no. 8  [PUBMED]  Medknow Journal
9.Prasad D, Jalali R, Shet T. Intracranial subfrontal schwannoma treated with surgery and 3D conformal radiotherapy. Neurol India 2004;52:248-50.  Back to cited text no. 9  [PUBMED]  Medknow Journal
10.Ahmad FU, Gupta A, Sharma MC, Shukla G, Mehta VS. The enigmatic origin of subfrontal schwannomas: Report of a case without hyposmia. Acta Neurochir (Wien) 2006;148:671-2.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]
11.Santosh K, Kesavadas C, Radhakrishnan VV, Thomas B, Kapilamoorthy TR, Gupta AK. Usefulness of T2*-weighted MR sequence for the diagnosis of subfrontal schwannoma. J Neuroradiol 2007;34:330-3.  Back to cited text no. 11    
12.Sabel LH, Teepen JL. The enigmatic origin of olfactory schwannoma. Clin Neurol Neurosurg 1995;97:187-91.  Back to cited text no. 12  [PUBMED]  [FULLTEXT]
13.Sano H, Hayashi Y, Hasegawa M, Yamashita J. Subfrontal schwannoma without hyposmia: Case report. Neurol Med Chir (Tokyo) 2004;44:591-4.  Back to cited text no. 13  [PUBMED]  [FULLTEXT]
14.Amador AR, Santonja C, Del Pozo JM, Ortiz L. Olfactory schwannoma. Eur Radiol 2002;12:742-4.  Back to cited text no. 14  [PUBMED]  [FULLTEXT]


  [Figure 1], [Figure 2a], [Figure 2b]

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