A 22-year-old woman presented with complaints of headache since four months and diminution of vision in the left eye since 1 ½ months. There was no history of vomiting or fever. On examination, she was conscious and oriented. Vision was 6/6 in the right eye; however, in the left eye, it was restricted to finger counting at two feet. Fundoscopy revealed bilateral papilledema. The other cranial nerves were normal. The rest of the neurological examination was unremarkable.

RADIOLOGICAL FINDINGS:

A CT scan revealed a large, well defined, lobulated, extraaxial, hyperdense mass lesion with few calcific foci within, measuring 7 x 5.7 x 5.6 cm - arising from the left middle cranial fossa and extending into the left temporo-parietal region causing effacement of the prepontine and basal cisterns.. There was mass effect on the left lateral ventricle and third ventricle. There was bony destruction of the floor of the middle cranial fossa, greater wing of sphenoid, the squamous plate of left temporal bone and anterior clinoid process on the left side.

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A plain and contrast enhance MRI scan was performed next. This showed an approximately 5.5 x 5.2 x 5 cms, lobulated extra-axial mass lesion arising from the left sphenoid wing. The lesion was hypointense on T2W and isointense on T1W images. It showed intense post contrast enhancement. Multiple hypointense specks were seen within it suggestive of calcific areas. Encasement of the left MCA and its branches was noted. It extended into the left parietal region with a CSF cleft adjoining it .Medially, it reached the lateral wall of left cavernous sinus. Anterosuperiorly, it extended up to the orbital apex. Laterally, it caused erosion of the overlying temporal bone. It was associated with perilesional edema causing mass effect on the ipsilateral lateral ventricle & minimal subfalcine herniation.

These features suggested a diagnosis of meningioma arising from the left sphenoid wing.

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Fig. 8

Total excision of left temporal extradural mass was done.

Histopathological findings of the tumor showed spindle cells and osteoblastic giant cells with areas of hemorrhage .There was no nuclear atypia .A diagnosis of giant cell rich neoplasm was suggested.

Fig. 9

Final Diagnosis :

Giant cell tumor of greater wing of left sphenoid bone.

DISCUSSION:

A giant cell tumor is a neoplasm that originates from non-bone forming supportive connective tissue of the marrow. This highly vascular lesion is composed of spindle shaped stromal cells interspersed among multinucleated giant cells.

Incidence:

Giant cell tumor of bone is a relatively common primary neoplasm accounting for 5-8% of all primary malignant bone tumors and 15% of all primary benign bone tumors. The usual age range is 20-40years. Benign tumors predominate in female patients in a proportion of 3:2; the malignant tumors show a predilection for the male patient in a ratio of 3:1

Location :

The most common sites are the distal femur, proximal tibia, distal radius and proximal humerus in decreasing order of incidence. The sacrum is the most commonly involved bone in the spine, representing 8% of cases. Other infrequent sites are the calcaneus, rib, carpal bones and patella. The skull is a rare location for GCT. In the cranium, the sphenoid bone is the commonest site followed by the temporal bone. This can be explained by the fact that the tumor genesis occurs in endochondral bone instead of intramembranous bone. The temporal bone has two main components - squamous and petromastoid. The squamous portion develops by intramembranous ossification, while the petreomastoid portion develops from cartilage (endochondral bone). GCTs are commonly seen to arise from the petromastoid portion.

Presentation :

Typically, the tumor presents as an enlarging mass associated with local pain. The tumor typically grows over a period of few weeks to years. Sign and symptoms associated with this tumor are more closely related to its location than to the characteristic of this tumor. GCT of the sphenoid may present with headache, visual field defects, blindness, diplopia, second through eighth cranial nerve dysfunction, endocrinopathy and change of mental status.

Radiological findings

Plain radiograph:

The radiographic appearance of giant cell tumor is characteristic. It is eccentric, metaphyseal radiolucent lesion of bone. Most lesions begin in the metaphysis and subsequently extend to the subarticular location, once the epiphyseal line has closed. Significant bone expansion with the production of a soap bubble appearance is noted that represents reactive trabecule formed by appositional growth that is usually located peripherally. The cortex is thinned and expanded and the endosteal margins show a narrow zone of transition. If the tumor is very aggressive, a purely lytic, radiolucent lesion will be seen with cortical breakthrough and the development of a soft tissue mass.

Giant cell tumors of the skull bone do not show any unique radiologic features that enable definitive diagnosis. A GCT usually presents as a purely lytic lesion and cannot be generally differentiated from other radiolucent lesions. Cortical break through with soft tissue expansion is common.

Cross sectional imaging:

Cross sectional imaging helps in delineating the extent of tumor. Computed tomography better delineates the osseous margins of the lesion and the status of the cortex. The expanded and thinned cortex is seen and presence or absence of matrix calcification can be assessed. MRI is currently the best imaging modality for giant cell tumor because of its superior contrast resolution and multiplanar imaging capabilities that allow accurate tumor assessment. MRI is useful in determining extra osseous extent and articular surface involvement; however, subtle cortical destruction is better demonstrated by CT.
GCTs show low intensity on T1W and heterogenous signal intensity on T2W images. Therefore, intramedullary tumor is best seen on T1W, while its extraosseous portion is best appreciated on T2W images
Gadolinium enhancement reveals areas of hypervascularity and enhancement with a very heterogenous signal pattern.

In our case, a radiological diagnosis of a meningioma was made. Meningiomas show following features:
NECT scan typically shows a sharply circumscribed, round or smoothly lobulated mass that abuts a dural surface - usually at an obtuse angle.
Approximately, 70% to 75% meningiomas are homogenously hyperdense relative to adjacent brain; 25% appear isodense. Hypotenuse tumours are seen in 1% to 5% of cases. Calcification is seen in 20% to 25% and can be diffuse or focal. Psammomatous (sand-like), sunburst, or globular and even rim-like patterns occur. Occasionally, meningiomas appear densely calcified.
Hyperostosis can be striking or absent. Bone destruction may sometimes be seen. Gross hemorrhage is uncommon. Although true cystic meningiomas with large intratumoral fluid-filled cysts are uncommon, small areas of non-enhancing areas of cystic changes or necrosis are seen in 8% to 23% of cases.
Degenerative brain parenchymal cysts and trapped arachinoid with pools of CSF between the meningioma and adjacent brain are common findings. Peripheral edema is seen in 60% of cases and may be extensive.
CECT scan shows intense, relatively uniform enhancement in 90% of all cases.10% to 15% of meningiomas have an atypical pattern with rim like tumor enhancement or imaging findings that suggest hemorrhage, prominent cyst formation, or metaplastic changes.
MR shows imaging findings that are characteristic for all extraaxial masses, like gray white interface "buckling" or displacement and a cleft or pseudocapsule of CSF and vessels that surrounds the mass, separating it from brain
Regardless of histologic type, most meningiomas are iso or slightly hypointense relative to cortex on T1 weighted studies, although signal on T2 is variable.
The prominent radial or sunburst vascular pattern is seen at cerebral angiogram. In others the dural and pial supplied portions of the tumor vary slightly in intensity.
A CSF cleft is often present around the meningioma, demarcating brain tumor interface and conforming its extraaxial location.
Contrast enhanced MRI is particularly useful in detecting small, inconspicuous meningiomas that are isointense with adjacent cortex on all pulse sequences. Post contrast study can also delineate the precise extent of en plaque lesion.
Sixty percent of meningiomas have a collar of thickened; enhancing tissue that surrounds their dural attachment .This is called as dural tail. The "dural tail sign" is highly suggestive but not specific for meningioma.