Indian Journal of Pathology and Microbiology

: 2020  |  Volume : 63  |  Issue : 3  |  Page : 445--448

Intracranial bony ball – An ossified variant of meningioma

Gayathri Priyadharshini1, Manjiri Phansalkar1, Dilip Phansalkar2, Vellore Seetharam Hari3,  
1 Department of Pathology, Pondicherry Institute of Medical Sciences, Kanagachettikulam, Puducherry, India
2 Department of Radiology, Pondicherry Institute of Medical Sciences, Kanagachettikulam, Puducherry, India
3 Department of Neurosurgery, Pondicherry Institute of Medical Sciences, Kanagachettikulam, Puducherry, India

Correspondence Address:
Gayathri Priyadharshini
Department of Pathology, Pondicherry Institute of Medical Sciences, Kanagachettikulam, Puducherry


An ossified variant of meningioma in the intracranial region is very rare. We report a case of a 28-year-old female who presented with headache for 4 years. Imaging revealed an extra-axial calcified mass in the left parieto-occipital lobe. The differential diagnosis included osteoblastoma both intracranial and periosteal, calcifying pseudotumor of the neural axis, hyperostosis of the cranium, and ossifying fibroma. She underwent excision of the calcified space occupying lesion. Histopathology was suggestive of an ossified meningioma. At the end of 2-year follow-up, she was asymptomatic with no signs of recurrence.

How to cite this article:
Priyadharshini G, Phansalkar M, Phansalkar D, Hari VS. Intracranial bony ball – An ossified variant of meningioma.Indian J Pathol Microbiol 2020;63:445-448

How to cite this URL:
Priyadharshini G, Phansalkar M, Phansalkar D, Hari VS. Intracranial bony ball – An ossified variant of meningioma. Indian J Pathol Microbiol [serial online] 2020 [cited 2020 Oct 24 ];63:445-448
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Meningiomas are tumors arising from the arachnoidal cells accounting for 20% of CNS tumors.[1] Metaplastic meningioma is a rare subtype of grade I benign meningioma with various mesenchymal differentiation such as osseous, cartilaginous, myxoid, xanthomatous, and lipomatous tissue. An ossified variant of meningioma is very rare accounting for only 1% of meningiomas.[2] It is reported in the intracranial and spinal region. Intracranial location is very uncommon. We report a rare such case of intracranial ossified meningioma in a 28-year-old female.

 Case History

A 28-year-old female presented to our hospital with complaints of headache for 4 years. The headache lasted for about 10–15 min and was aggravated on severe work. There was no history of nausea, vomiting, loss of consciousness, or seizures. There was no significant past history of any other major illness. On examination, her higher functions were normal. There was no cranial nerve or spinal motor or sensory deficit. Her blood investigations were within normal limits. Computer tomography of the brain showed a large multilobulated hyperdense calcified lesion in the left parieto-occipital lobe. The lesion was seen separate from occipital lobe inner dipole. There was mild hypodensity seen adjacent to the lesion. These findings were suggestive of osteoma or calcified meningioma [Figure 1]. Magnetic resonance imaging of the brain revealed a lobulated extra-axial heterogeneous intense lesion in the left parieto-occipital convexity which showed buckling of adjacent gray-white matter measuring 3 × 3.3 × 1.9 cm in craniocaudal, anteroposterior, and mediolateral dimensions. There was a patchy enhancement of the lesion following intravenous contrast administration. The lesion showed diffuse calcification with denser calcification in the center. There was no evidence of hyperostosis of the bone. These features were suggestive of meningioma [Figure 2].{Figure 1}{Figure 2}

She was planned for operative management. Under general anesthesia, in lateral position, patient underwent left occipital craniotomy with excision of the calcified space occupying lesion. Intra-operatively, she had a hard calcified nodule of 3 × 2 × 2 cm extra-axially over the occipital region attached by a few fibrous strands to the duramater and a few feeding vessels from the occipital cortex. The excised specimen was sent for histopathology.

Macroscopically, the specimen showed a single bony hard nodular mass with a gray-white translucent surface measuring 3 × 3 × 1.5 cm. Microscopically, the section showed an encapsulated lesion composed of interlacing trabeculae of osteoid and osseous tissue set in the scanty fibrocollagenous vascularized stroma. Thin rim of myxoid tissue under the capsule as well as foci of myxoid degeneration in the stroma was noted. Osseous tissue was predominantly of woven bone type. However, few areas showed lamellar bone. Osteoblastic rimming, as well as few osteoclastic cells, was seen in foci. Occasional foci in the stroma showed compactly arranged plump cells with whorling suggestive of meningeal cells. A focus of compact meningothelial cells with psammoma bodies was noted in the capsule with adherent brain tissue in the vicinity [Figure 3], [Figure 4], [Figure 5], [Figure 6]. All these features helped in the diagnosis of ossified meningioma (metaplastic meningioma) by ruling out the possibility of osteoma.{Figure 3}{Figure 4}{Figure 5}{Figure 6}

Postoperatively her neurological status was intact. At the end of 2-year follow-up, she was asymptomatic with no signs of recurrence.


Meningiomas are tumors arising from the arachnoidal cells, which line the outer layer of the arachnoid mater. They account for 20% of the brain and spinal cord tumors.[1] They show vast diversity histologically. Intracranial tumors are frequently seen in cerebral convexities, falcine or parasagittal areas, sphenoid ridge, tuberculum sellae, and parasellar region.

Meningiomas with osseous tissue in the tumor parenchyma are named as osseous or ossified meningioma. Ossified meningiomas belong to metaplastic meningioma, which itself is a rare subtype of meningioma. Lambert Rogers in 1928 was the first to report ossified meningioma in the spinal cord.[3] They account for 1% of all meningiomas.[2] They are usually located on the cerebral convexities, Sylvian fissure, or spine. Involvement of the ventricular system has also been reported. Very few cases of ossified meningioma have been described in literature till now.[1],[2],[3],[4],[5] Intracranial location of osseous meningioma is very rare.

The exact etiology for ossification is unknown. Few theories have been described for the mechanism of ossification. One among them is that the ossification is secondary to metaplasia of arachnoidal or interstitial cells. Role of alkaline phosphatase in the mechanism of ossification has also been mentioned in the literature. According to Uchida et al.,[6] ossification is secondary to exposure to biochemical activity in the ossification cascade. Ossification may be secondary to long-standing calcification.

Tang et al.[1] reported 15 cases of metaplastic meningiomas. In their series, the clinical presentations were headache, dizziness, seizure, disturbance in vision, and weakness of lower limbs. The most common locations were convexities of the brain and spinal cord. Among 15 cases, 9 of them had osseous or cartilaginous tissue. Radiology showed calcification in only four cases in computed tomography (CT) scan and heterogeneous enhancement in only three cases in contrast magnetic resonance imaging (MRI). The present patient had only headache with the presence of calcification in CT scan and heterogeneous enhancement in MRI.

Baressi et al.[2] reported seven cases of osteoblastic meningiomas out of which five were intracranial, one was spinal, and one was intraventricular. All of them were females. Clinically, four of them presented with headache and three of them presented with hyposthenia. CT and MRI revealed a calcified mass in all cases. Tai et al.[5] reported a case of ossified meningioma with intratumoral hemorrhage.

Differential diagnosis included osteoma, osteoblastoma both intracranial and periosteal, calcifying pseudotumor of the neural axis, psammomatoid meningioma, and ossifying fibroma. Radiologically, osteomas lack contrast enhancement whereas meningiomas show contrast enhancement. Histopathologically, the presence of abundant adipose tissue within the intertrabecular marrow space is diagnostic of osteomas. Microscopically, osteoblastoma shows interanastamosing osteoid and bony trabeculae within the loose fibrovascular stroma. The trabeculae are usually lined by a single layer of osteoblasts. Meningioma cells as such may become osteoblasts following metaplasia. These osteoblasts may be responsible for the ossification in the tumor. Psammomatoid meningioma is differentiated from osseous meningioma by the lack of osteoblasts and osteoclasts rimming around the psammoma bodies. These are termed as “metaplastic,” because transformed tumor cells demonstrate the characteristic histological features of the cell they mimic. Treatment of these tumors is surgical excision.

To conclude, ossified meningioma is a rare entity and intracranial location per se is very rare. Clinicoradiological findings and histopathology play a very important role in the diagnosis of this condition. Early diagnosis and excision of the lesion result in a good prognosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

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