| Abstract|| |
Mixed tumors composed of schwannoma and meningiomas are extremely rare and are usually associated with neurofibromatosis-2 (NF-2). So far, all the cases reported have involved the cerebello-pontine angle. Only two cases did not have a clear association with NF-2. We report a mixed tumor comprising of meningioma admixed with schwannoma in a 33-year-old male with bilateral trigeminal nerve schwannomas. The patient did not fit the existing diagnostic criteria of NF-2. The relevant literature, along with diagnostic criteria for NF-2 is discussed.
Keywords: Bilateral schwannoma, meningioma, mixed tumor, neurofibromatosis-2, schwannoma, trigeminal nerve
|How to cite this article:|
Jain A, Suri V, Sharma BS, Sharma MC. Mixed schwannoma with meningioma of the trigeminal nerve. Indian J Pathol Microbiol 2010;53:769-71
| Introduction|| |
The co-existence of schwannoma and meningioma as a mixed intracranial tumor is a rarity usually seen in association with neurofibromatosis type 2 (NF-2).  Only 10 cases have been described so far in literature. ,,,,,, The most common site of involvement is in the cerebello-pontine angle (CPA), involving the vestibular nerve. Involvement of the trigmenial nerve has never been reported previously. We present a mixed tumor comprising of distinct schwannoma and meningioma components within the same tumor, arising from the trigeminal nerve, and review the relevant literature.
| Case Report|| |
A 33-year-old male presented with complaints of redness of the right eye, episodic diplopia, and numbness of the right side of face since two months. There was no history of seizure, ear discharge, visual deterioration or loss of consciousness. On examination there was reduced right sided blinking response, reduced sensation on the right side of face (about 30-40%), and weakness with atrophy of the right side jaw muscles. Patient's visual acuity was normal and there was movement of the extra-ocular muscles. On systemic examination, no subcutaneous nodules were identified. There was no family history of neurofibromatosis.
Computerized tomography (CT) scans showed a right sided extra-axial medial temporal region hypo dense mass. A similar small mass was seen on the left side. Contrast enhanced magnetic resonance imaging (MRI) [Figure 1] revealed bilateral parasellar masses (larger on right side) abutting bilateral body and lower wing of sphenoid and extending to the anterior aspect of the petrous apex. The masses were hypo intense on T1 weighted images and hyper intense in T2 with contrast enhancement. For the right sided mass, a right pterional craniotomy and excision of tumor by sub-temporal, intra-dural approach was performed. Intra-operatively, a tumor of variable color and consistency was identified arising form the Vth nerve. The color ranged form creamy white to grayish with areas of fibrosis and old hemorrhage, and a soft to firm consistency.
|Figure 1 :Contrast MRI brain (a) sagittal and (b) axial, showing bilateral parasellar masses; right sided lesion showing medial portion of homogenous enhancement and lateral heterogenous enhancement|
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A clinical diagnosis of a schwannoma arising from the bilateral Vth cranial nerve (CN) was made. Further course in hospital was uneventful and by the time of discharge the patient had up to 50% recovery of the right sided sensory loss. For the left sided small asymptomatic tumor a gamma knife ablation therapy after three months follow-up was advised.
The tumor was received for histopathology in multiple pieces measuring together 4×2×1 cm and was processed in entirety. In all the sections, the tumor was composed of two distinct populations of cells. In some areas the tumor demonstrated typical features of a schwannoma [Figure 2]a comprising of interlacing bundles of spindle cells, with focal compact areas showing nuclear palisading (Antoni A areas) and less cellular loosely textured areas with indistinct processes (Antoni B). Verocay body formation was seen consisting of alternating, parallel rows of tumor cell nuclei and their densely packed, aligned cell processes. In other areas, a second component was identified comprising of numerous concentric lamellated psammoma bodies and uniform cells with moderately abundant eosinophilic cytoplasm, round to oval nuclei with delicate chromatin, with some nuclei showing central clearing and occasional nuclear grooves. Focally, these cells were arranged in the form of whorls. This component resembled a transitional meningioma in appearance [Figure 2]b. No mitosis or necrosis was seen in any of the components. Focal areas of hyalinization were identified in the meningothelial areas. On performing immunohistochemistry, the meningioma component was strongly immunopositive for epithelial membrane antigen (EMA) [Figure 2]c while the benign nerve sheath tumor (schwannoma) component was strongly immunopositive for S100 protein [Figure 2]d. MIB-1 labeling index (calculated on counting 1000 nuclei) was 2-3%. Based on these features, a diagnosis of a mixed tumor comprising of meningioma with schwannoma of the right side Vth cranial nerve was proffered.
|Figure 2 :(a) Elongated cells with nuclear pallisading (Antoni A areas) forming Verocay bodies in shwannoma areas (H and E, ×200); (b) Meningioma area with meningothelial cells in whorls and fascicles, psammomatous calcification and hyalinization (H and E, ×100). Inset: Inset shows clusters of meningothelial cells in whorls seen at higher magnification. (H and E, ×400); (c) EMA positivity in meningothelial cells. Foci of hyalinization are negative (DAB, ×400). Inset: negativity for EMA in schwannoma areas (DAB, ×400); (d) Strong S-100 positivity in the schwanninan component (DAB, ×200)|
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| Discussion|| |
Neurofibromatosis-2 (NF-2) is a rare disease affecting about 1 in 40000 newborns  and has an autosomal dominant inheritance. NF-2 associated schwanomas usually present at an earlier age (third decade) than sporadic vestibular schwannomas (sixth decade). According to the currently followed diagnostic criteria, a definite diagnosis of NF-2 requires either bilateral vestibular schwannomas; or a first degree relative with NF-2 and either a unilateral vestibular schwannoma at < 30 years age, or any two of meningioma, schwannoma, glioma, posterior subcapsular lens opacity.  A diagnosis of probable NF-2 also requires a unilateral vestibular schwannoma at <30 years with any of the above tumors or multiple meningiomas with either unilateral vestibular schwannoma at < 30 years or one of the above tumors. Although CN schwannomas, except for CN VIII schwannomas, also occur spontaneously, they are relatively rare. Thus, the presentation of any patient with multiple CN schwannomas prompts a screening for NF2. Till date of the 10 cases reported in literature of a mixed schwannoma and meningioma in the same tumor [Table 1], eight cases had an association with NF-2. ,,,, Our patient, 33 years old, had bilateral schwannomas of the trigeminal nerve and one of the schwannomas had a mixed meningioma component. Thus, histologically with the coexistence of an admixed schwannoma and meningioma in a 33-year-old, NF-2 cannot be completely ruled out. However, there was no history of NF-2 in the family, no subcutaneous nodules or skin lesions, and no vestibular nerve involvement. On screening, no other intracranial or spinal tumor was identified. Similar to our case, the cases reported by Ludemann et al. and Chen et al.  also did not fulfill the current diagnostic criteria laid down for NF-2. Baser et al. evaluated the existing diagnostic criteria for NF-2 and concluded that none of the existing sets of criteria are adequate at initial assessment for diagnosing people who present without bilateral vestibular schwannomas as having NF2, particularly people with a negative family history of NF2. They further recommended that a single, revised set of diagnostic criteria should be devised to replace all of the existing sets of criteria. In the present case, the patient was advised a strict follow up for early detection of any other lesion or tumor which might fall into the currently accepted criteria of NF-2.
|Table 1 :Summary of mixed schwannoma with meningioma cases reported including the present case |
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Though several other cases of a concurrent and adjacent schwannoma and meningioma ("collision tumors") have also been described, a "pure" mixed tumor with coexistence of distinct areas of these two components within the same tumor is a rarer entity. 
Various explanations have been put forward to explain the possible mechanisms of tumorigenesis in such mixed tumors. Kim et al.  proposed two mechanisms of histogenesis, one being a "collision" of two different tumors developing independently at the same anatomical site, with the one which developed earlier extended into the other to encase it. The second possibility they proposed was a bidirectional differentiation from a common progenitor cell. They further suggested that the first hypothesis appears far more likely on biological and molecular genetic grounds. However, as they stated, for such a hypothesis, there has to be a distinct dividing plane at the margins between the two tumor components, as was seen in their case. In our case and the case reported by Elizabeth et al. as well as Gelal et al. and Ludemann et al. there were intermixed areas of both the tumor components, with no clear line of demarcation between them. Hence, an alternative hypothesis proposed by Geddes et al., i.e. reactive meningothelial hyperplasia occurring adjacent to a schwannoma seems a more likely possibility. Further, Geddes et al. suggested that arachnoidal proliferation appears to be more exuberant in bilateral acoustic neurofibromatosis than in sporadic acoustic schwannomas, possibly the result of a disease-related growth factor being produced by schwann cells.
To conclude, this is the first case of a mixed meningioma and schwannoma involving the trigeminal nerve and the third with a presumptive diagnosis of NF-2. The presence case highlights the rare occurrence of this tumor outside the cerebllopontine angle and without a definite diagnosis of NF-2.
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Department of Pathology, AIIMS, New Delhi-110 029
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]