Primary intraosseous osteolytic meningioma: a case report and review of the literature

Background Primary intraosseous meningioma is a subset of extradural meningioma that arises in the bone, and only a few cases have been reported to date. Case presentation An 80-year-old man presented with decreased hearing on the right side accompanied by a disturbance of balance 10 months prior to admission. Magnetic resonance imaging revealed an 8 × 7 cm osteolytic mass in the right posterior fossa related to the petrous bone, with extension to the cervical region. During surgery, the tumor was found to be located extradurally, with no invasion of the dura. The tumor was removed entirely, apart from a small portion around the jugular foramen to avoid lower cranial nerve injury. Conclusion The final diagnosis was primary intraosseous osteolytic meningioma with atypical pathology. Here, we report a rare case of an osteolytic skull lesion in the skull base not invading the dura and with extensive bone destruction. Electronic supplementary material The online version of this article (10.1186/s12883-019-1392-5) contains supplementary material, which is available to authorized users.


Background
Meningiomas are common intradural lesions that arise from the arachnoid cap cells of the arachnoid layer. In contrast, primary extradural meningioma is a relatively rare entity, accounting for less than 2% of all meningiomas [1,2]. They may arise from other locations, such as the skin, orbit, nasopharynx, and neck [3][4][5]. Primary intraosseous meningioma, which arises in the bone, is a subset of primary extradural meningioma, and only a few cases have been reported [1,3]. Here, we report a recent case of primary intraosseous osteolytic meningioma with extension to the cervical region which was successfully removed.

Case presentation
An 80-year-old man presented with a progressive decrease in hearing on the right side accompanied by dizziness and disturbance of balance 10 months prior to admission. The neurological examination revealed right hypoglossal nerve palsy. Audiometry documented complete sensorineural hearing loss on the right side. Skull x-ray and cranial computed tomography (CT) scans showed a large osteolytic lesion with bone destruction, including the temporal bone, occipital bone, clivus, jugular foramen, and hypoglossal canal ( Fig. 1a and b). Magnetic resonance imaging (MRI) revealed an 8 × 7 cm homogeneous enhancing mass in the right posterior fossa related to the petrous part of the temporal bone, with extension to the cervical region (Fig. 1c). The cerebellum was displaced, and definite brain invasion was not seen. The preoperative diagnosis was a temporal bone origin malignancy such as squamous cell carcinoma or meningioma with invasion of the petrous bone.
The patient underwent surgery to obtain a pathological diagnosis and for complete removal of the mass. A C-shaped postauricular skin incision was made that extended to the neck. The scalp was reflected anteriorly, and the mass infiltrating the subcutaneous tissue was exposed. The lesion appeared as a firm gray mass that had destroyed the temporal and occipital bones. The dura was intact with no invasion, and the lesion was easily peeled off. For the cervical part of the tumor, the major vessels were secured inferiorly, and the mass was removed up to the skull base. The tumor was removed entirely, except for a small portion around the jugular foramen to avoid lower cranial nerve injury. Finally, the large empty space was filled with a sternocleidomastoid muscle flap (Fig. 2). There were no neurological deficits after surgery.
Histopathological studies confirmed a WHO (World Health Organization) grade II atypical meningioma with up to 6 mitoses per 10 high-power fields (Fig. 3). The Ki-67 proliferation index was 15%. The results of immunohistochemical staining are provided in Additional file 1: Figure S1.

Discussion and conclusions
Primary intraosseous meningiomas are rare cranial lesions that arise from the bone, and they represent the most common type of primary extradural meningiomas [1][2][3]. The majority of intraosseous meningiomas are osteoblastic and cause hyperostosis, which may mimic fibrous dysplasia. In contrast, and more rarely, they may present as an osteolytic skull lesion [6,7]. Reportedly, less than 20% of intraosseous meningiomas are osteolytic [8].
Primary extradural meningiomas are most commonly found in skull convexities, the paranasal sinus, and the middle ear but rarely in the skull base. Liu et al. reported 170 cases of extradural meningiomas in the head, and only 5.8% were located in the skull base [9]. Notably, there are few reports of osteolytic intraosseous meningiomas in the skull base. To date, 50 cases of osteolytic subtypes (including the present case) have been reported in the English literature (Table 1). Of these, only seven were located in the skull base, and all but two originated from the petrous bone.  The exact origin of extradural meningiomas is unclear, but several theories have been proposed. Their unusual locations are assumed to be the result of the aberrant differentiation or misplacement of undifferentiated mesenchymal stem cells [51]. Alternatively, extradural meningiomas may arise from differentiated arachnoid cap cells associated with blood vessels or nerves traversing the skull [52,53]. Another theory proposes that they originate from arachnoid cap cells that get trapped in the cranial sutures during embryogenesis or molding of the cranium at birth [20,21,54]. Trauma with skull fracture has also been proposed as a causative factor of some extradural meningiomas, suggesting direct dural entrapment within bone fragments at the time of trauma [55].
The osteolytic subtype of intraosseous meningiomas is often misdiagnosed as a primary or secondary bone tumor due to its radiological appearance. The differential diagnosis of a solitary osteolytic skull lesion includes hemangioma, chondroma, chondrosarcoma, eosinophilic granuloma, epidermoid cyst, giant cell tumor, myeloma, and metastatic skull tumor [6,23,33].
Primary extradural meningiomas were practically classified according to their location by Lang and colleagues ( Table 2) [3]. Therefore, intraosseous meningiomas could be considered Type II or Type III extradural meningiomas. Based on this classification, the present case falls into the type IIIB category due to the presence of extracalvarial extension. This classification is helpful in predicting the risk of tumor recurrence. The IIC and IIIC subtypes rarely recur after complete resection, whereas the IIB and IIIB subtypes have a reported lifetime risk of recurrence of 26% [3].
Histopathological features are also important factors affecting tumor recurrence and prognosis. Recurrence was noted in 22% of benign intraosseous meningiomas in the literature, while it was reportedly 33% in cases of tumors with atypical or malignant pathology. In addition, aggressive atypical or malignant meningiomas had a significantly higher mortality of 29% compared to tumors with benign features (4.8%) [3]. Osteolytic meningiomas may have a higher incidence of atypical or malignant features [6]. In previous reports, benign features were reported in 87-89% of all extradural meningiomas, whereas in our literature review of osteolytic intraosseous meningiomas, 26% of cases were WHO grade II or III [3,8]. Wide surgical excision is the main treatment for extradural meningiomas, and it is potentially curative if complete resection is achieved [6,7]. In the present case, a small portion of the tumor near the jugular foramen could not be removed due to the possibility of cranial nerve injury. In the case of skull base lesions that cannot be totally resected, decompression of vital neural structures is performed.
In conclusion, we performed surgical treatment for a rare case of primary osteolytic intraosseous meningioma in the skull base with extension to the cervical area. The histopathologic diagnosis was atypical meningioma. If possible, complete resection is the treatment of choice, and serial follow-up should be done to confirm recurrence or progression.   Additional file Additional file 1: Figure S1.