| Abstract|| |
Intracranial meningiomas are not often aspirated unless they erode the skull and present as swelling in the head and neck region. We describe the cytologic findings of fine needle aspiration cytology in a clear cell variant of intracranial meningioma presenting with swelling in the left parietal region of the scalp in a 45-year-old woman. The diagnosis was confirmed by histopathology. Clear cell meningioma is characterized by patternless sheets of clear polygonal cells. Clear cell meningioma is a rare distinctive cytological subtype of meningioma with high recurrence rate and increased mortality, which necessitate frequent follow-up after surgical excision. The recognition of clear cell meningiomas is important here and should be distinguished from other clear cell lesions of the scalp. If clear cell epithelial neoplasm is encountered on fine needle aspiration, it is reasonably possible to provide at least a differential diagnosis of meningioma based upon the focal whorls, sparce vascularity on low magnification, along with the presence of pseudoinclusion and inconspicuous nucleoli at high magnification.
Keywords: Clear cell; meningioma; scalp; fine needle aspiration cytology
|How to cite this article:|
Jayasree K, Divya K N. The cytology of intracranial clear cell meningioma with an unusual scalp presentation. J Cytol 2011;28:117-20
|How to cite this URL:|
Jayasree K, Divya K N. The cytology of intracranial clear cell meningioma with an unusual scalp presentation. J Cytol [serial online] 2011 [cited 2020 Feb 21];28:117-20. Available from: http://www.jcytol.org/text.asp?2011/28/3/117/83469
| Introduction|| |
Clear cell meningioma is a rare, intrinsically aggressive variant of meningothelial neoplasm consisting of patternless sheets of clear polygonal cells with bland-appearing nuclei. These tumors have a clinicopathological resemblance to other clear cell lesions like metastatic renal cell carcinoma.
The cytological features of a case of intracranial clear cell meningioma with an unusual scalp presentation are presented here.
| Case Report|| |
A 45-year-old woman presented with a swelling over the left side of the scalp of one-year duration with intermittent headache. Local examination revealed a diffuse, ill-defined, immobile, soft, non-tender swelling measuring 5 × 3 cm in the subcutaneous plane over the left parietal region of the scalp. The general physical and the systemic examinations were normal. The routine hematologic and urine examinations were normal. But the liver function tests revealed increased enzyme activity. Ultrasound examination to rule out abdominopelvic pathology was normal. Computerized tomographic (CT) carotid angiography showed a large well-defined irregular intensely enhancing space occupying lesion involving the juxtacortical aspect of the left frontoparietal region, with complete destruction of the underlying bone with speculated margins and the dilated left superficial temporal artery feeding the lesion [Figure 1]. Differential diagnoses of malignant meningioma and metastatic deposits were suggested.
|Figure 1: Neuroimage of CT carotid angiography showing an irregular intensely enhancing space occupying lesion involving the juxtra cortical aspect of the left frontoparietal region with destruction of the underlying bone with speculated margins and dilated left superficial temporal artery feeding the lesion|
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Fine needle aspiration cytology of the scalp swelling was done using a 24-gauge needle and 10-mL syringe to obtain a cellular aspirate. The smears were stained with hematoxylin and eosin (H and E) and May-Grünwald-Giemsa stains. The smears were highly cellular, populated by a mixture of meningothelial and clear cells arranged as diffuse sheets, scattered single cells and cohesive clusters, some seen as small tight whorls [Figure 2]. The meningothelial cells had pale pink granular cytoplasm, indistinct cytoplasmic borders, round to oval nuclei and inconspicuous nucleoli. Few cells showed nuclear pseudoinclusions [Figure 2]. The clear cells were polygonal with abundant clear cytoplasm, ovoid nucleus, evenly distributed chromatin and inconspicuous nucleoli [Figure 2]. Capillaries were not seen. Differential diagnoses of clear cell tumors of scalp-like metastatic renal cell carcinoma, meningioma, malignant melanoma and skin adnexal tumor were thought of. The CT angiography findings, mixture of meningothelial cells and clear cells focal whorls on cytology favored the opinion of a possibility of meningioma to be suggested. The clear cells with inconspicuous nucleoli and the paucity of capillaries differentiated this lesion from metastatic renal cell carcinoma [Figure 2]. The patient underwent extensive resection of the tumor and the specimen was subjected to histopathological examination. Gross examination revealed multiple fragments of friable grey white tissue mixed with blood clots, largest measuring 2.5×1.2 ×1cm.
|Figure 2: Smear shows meningothelial cells and clear cells. Inset (lower right) shows whorls and inset (lower left) shows pseudoinclusion. (MGG × 400, H and E × 400), inset (upper right and left) shows predominantly clear cells in patternless pattern with nucleus having inconspicuous nucleoli and paucity of capillaries (Hand E, × 400)|
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Microscopic examination showed a neoplasm composed of a mixture of patternless sheets of meningothelial cells and clear cells, focally forming whorls at places [Figure 3]a. The meningothelial cells had round to oval nuclei, inconspicuous nucleoli with moderate to abundant eosinophilic cytoplasm and indistinct cytoplasmic borders. The clear cells were polygonal with abundant clear cytoplasm indicating high glycogen content and vesicular nucleus and inconspicuous nucleoli [Figure 3]b. These cells were traversed by collagen bands. There was paucity of capillaries. Mitotic activity was not increased. Necrosis was absent. The neoplasm was seen infiltrating into the surrounding tissue and bone. A histological diagnosis of clear cell meningioma (WHO gradeII) was made. Immunohistochemical analysis of the tissue was done and was found positive for epithelial membrane antigen [Figure 4]. The diagnosis of clear cell meningioma was confirmed.
|Figure 3: (a) Section shows meningothelial cells in whorls and psammoma bodies (H and E, × 100); (b) Section shows patternless sheets of clear cells (H and E, × 400)|
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|Figure 4: (a) Section showing IHC positive for EMA in meningothelial cells (Peroxidasse-antiperoxidase stain, x100); (b) Section showing IHC positive for EMA in whorls (Peroxidasse-antiperoxidase stain, x100); (c) Section showing IHC positive for EMA in meningothelial cells (Peroxidasse-antiperoxidase stain, x400); (d) Section showing IHC positive for EMA in whorls (Peroxidasse-antiperoxidase stain, x400)|
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| Discussion|| |
The meningiomas are slow-growing mesenchymal neoplasms of central nervous system (CNS) usually attached to the dura, arising from the meningothelial cell of the arachnoid. They account for 24% of primary CNS tumors. 
Most meningiomas are encountered in middle or late adult life.  They also appear during childhood and adolescence. These tumors show a moderate female predominance with a female to male ratio of 3:2. 
Meningiomas are intracranial, occurring throughout the craniospinal axis, dura-based, found along any of the external surfaces of brain as well as within the ventricular system. Meningiomas also occur ectopically, located entirely outside the craniospinal confines, encountered in the head and neck region, cutaneous sites, lung and mediastinum. ,
Some intracranial meningiomas biologically behave as poorly delimited blanket-like growth, deflecting the adjoining neural tissue that insidiously permeate the neighboring skull provoking a highly characteristic form of osteoplastic expansion, when neglected come to attention as visible masses in the scalp.  Such meningiomas presenting extracranially, having a connection to the CNS, are called secondary meningiomas, similar to the one presented in our case. 
The typical meningioma displays a variety of distinctive cytohistologic patterns of which whorls formation is a characteristic feature which is evident at least focally.
The classification of meningioma recognizes 15 types encompassing three grades. The meningothelial, fibrous and transitional variants are the most common. According to their increasing biologic potential, these are classified as meningioma, atypical meningioma and anaplastic meningioma. 
Clear cell meningioma is a subset of meningothelial neoplasm with aggressive biological behavior. Clear cell meningiomas has a predilection for young subjects including children. Afourth ventricular presentation has been described as a bulbar example in a two-year-old child.  These tumors are usually extra-axial, dura-based, associated with cranial nerves, spinal roots or cauda equina. They are most often found in the spinal canal, cerebellopontine angle and foramen magnum. 
The cytology of clear cell meningiomas was described by Gyure et al.,  Imlay et al. and Miyuki et al. and are similar to the description in our case report. The classic meningothelial attributes, whorls and nuclear pseudoinclusions, may or may not be seen.  These tumors are characterized by high recurrence rates and increased mortality, despite the fact that most of them do not show conspicuously increased mitotic activity and necrosis.  The differential diagnosis of clear cell lesions in the scalp would include metastatic renal cell carcinoma, clear cell meningioma and other lesions like balloon cell melanoma, myoepithelial variant of sweat gland carcinoma, nodular hidradenoma and clear cell pilar tumor. 
Metastatic renal cell carcinomas (RCC) present with hematuria and renal mass on ultrasound - abdomen. Cytologically, they contain large polyhedral clear cells arranged in tubular and gland-like structures. The cells have large vesicular nucleus with prominent nucleoli and endothelial cells traversing the cell groups.
Balloon cell melanoma contains aggregates of balloon cells with abundant clear cytoplasm and little nuclear atypia, in addition to melanoma cells which are uniform with atypical hyperchromatic nuclei and abundant cytoplasm containing varying amounts of melanin in the form of dusty particles.
Nodular hidradenomas are subcutaneous cystic swellings containing clear polyhedral cells admixed with epidermoid cells. Clear cell pilar tumor is a subcutaneous lobular lesion composed of squamous epithelium.
Sweat gland carcinomas are subcutaneous swellings which show positivity for amylophosphorylase and succinic dehydrogenase.
RCC, which in the context of scalp mass, would mean stage-IV disease needing thorough urologic evaluation, whole body positive emission tomography (PET)-CT and metastasectomy. Clear cell meningioma, which would imply contiguous extension from dural mass that would need a properly planned neurosurgery. All other possibilities like skin tumors need a wide local excision which can be performed by a general or plastic surgeon.
In conclusion, clear cell meningiomas are rare, distinctive, intrinsically aggressive intracranial meningiomas with high recurrence rate and increased mortality that necessitate frequent follow-up after surgical resection. If clear cell epithelial neoplasm is encountered on fine needle aspiration, it is reasonably possible to provide at least a differential diagnosis of meningioma based upon the focal whorls, space vascularity on low magnification, along with the presence of pseudoinclusion and inconspicuous nucleoli at high magnification.
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Department of Pathology, Medical College (VIMS), Bellary - 583 104, Karnataka
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]