Meningioma is one of the most common intracranial tumors, accounting for approximately 13%–19% of all primary brain neoplasms, and arises from arachnoid cap cells of the meninges [1,2]. These tumors are typically benign and slow-growing. Although intracranial meningiomas are well recognized, extracranial presentations are rare [3].

Extracranial meningiomas most frequently occur in the head and neck region, including the scalp, temporal bone, nasal cavity, paranasal sinuses, orbit, and pterygopalatine fossa [4]. However, primary extracranial meningiomas may also arise in other unusual locations such as the lung, mediastinum, eyelids, digits, retroperitoneum, thigh, and foot [5].

Primary extracranial meningiomas account for only 1%–2% of all meningiomas and may therefore be easily misdiagnosed as other soft-tissue tumors [3,6]. In particular, occurrence in the temporal region without intracranial or dural involvement is uncommon, which can make preoperative diagnosis challenging.

Here, we report a rare case of primary extracranial meningioma arising in the temporal region of a 66-year-old woman that was successfully treated with complete surgical excision. In ad-dition, we review previously reported cases of extracranial meningioma in the temporal region to highlight the clinical characteristics, radiologic findings, treatment strategies, and outcomes associated with this rare entity.

A 66-year-old woman presented with a large mass in the left temporal region (Fig. 1). She first noticed the lesion 10 years earlier and reported no pain or restriction of mouth opening. Computed tomography (CT) revealed a mass measuring 2.1× 2.7×4.6 cm between the left temporalis muscle and the skull, with irregular osteolytic changes along the outer surface of the left frontotemporal and sphenoid bones. No intracranial lesion or radiologic evidence of dural continuity was observed (Fig. 2), and no regional lymph node enlargement was noted on physical examination or imaging.

Clinical suspicion of a muscle-origin sarcoma prompted fineneedle aspiration biopsy, which revealed a spindle-cell neoplasm. Given this finding, the possibility of a malignant soft-tissue tumor was considered during surgical planning. Complete excision of the mass was subsequently performed through a coronal scalp incision to achieve both a definitive diagnosis and total removal (Fig. 3). The surgical strategy aimed at en bloc resection along normal tissue planes, with careful dissection to achieve complete gross removal while preserving surrounding critical structures. Intraoperative frozen section biopsy was not performed, as the lesion was extracranial, showed no skin involvement, and lacked radiologic features suggestive of aggressive malignancy.

The tumor had an ill-defined margin and was carefully dissected, completely excised, and submitted to histopathological evaluation. Histopathological examination confirmed an extracranial meningioma (World Health Organization [WHO] grade II) with mildly increased cellularity, occasional nucleoli, and no necrosis. Immunohistochemistry revealed diffuse positivity for epithelial membrane antigen (EMA) and vimentin, with a low Ki-67 proliferation index (Fig. 4). The patient recovered without any functional deficits or postoperative complications. Postoperative magnetic resonance imaging (MRI) indicated no residual tumor, and adjuvant radiotherapy was not recommended.

Surveillance brain MRI was performed every 6 months (Fig. 5), with no recurrence or lymph node enlargement observed. At the 3.5-year follow-up, the patient remained in good condition, with no evidence of recurrence or disease progression (Fig. 6).

Primary extracranial meningiomas are rare tumors, accounting for only 1%–2% of all meningiomas [6-8]. Although most extracranial meningiomas arise in the head and neck region, they have been reported in a wide range of sites, including the scalp, paranasal sinuses, orbit, temporal bone, and infratemporal fossa [5,7-13]. Among these locations, the temporal region is particularly uncommon, especially when the lesion presents as a purely extracranial mass without dural attachment or intracranial communication [5,14-19]. This rarity contributes substantially to diagnostic uncertainty and explains why these lesions are often not suspected preoperatively.

Several hypotheses have been proposed regarding the pathogenesis of extracranial meningiomas, including ectopic arachnoid cell rests displaced during embryologic development, proliferation of arachnoid cells along cranial nerve sheaths, and mesenchymal metaplasia of pluripotent cells [12-14]. Of these, ectopic arachnoid cell rests remain the most widely accepted explanation for primary extracranial lesions. Clinically, extracranial meningiomas are classified as primary lesions, which arise outside the cranial cavity without intracranial continuity, or secondary lesions, which represent extracranial extension of an intracranial meningioma [6]. This distinction is important because primary lesions generally show more indolent behavior and may be adequately treated with local excision, whereas secondary lesions require careful assessment of associated intracranial disease.

Published reports of extracranial meningioma involving the temporal region have described lesions arising in the temporal bone, temporalis muscle, and infratemporal fossa [15-19]. Despite differences in anatomical origin, these tumors share several clinical features. Most patients present with a slowly enlarging painless mass, and symptoms are often minimal or absent until the lesion reaches a sufficient size to produce facial asymmetry, localized discomfort, or functional impairment such as trismus [7-9,17,19]. Because of their indolent growth and nonspecific presentation, delayed diagnosis is common, and these lesions are frequently mistaken for more common benign or malignant soft-tissue masses.

Radiologic evaluation is central to preoperative assessment, but imaging findings are rarely diagnostic. CT is particularly useful for identifying adjacent bony change, including hyperostosis or osteolytic erosion, whereas MRI is essential for defining soft-tissue extent and excluding intracranial extension or dural involvement [5,15]. A well-circumscribed soft-tissue mass abutting the skull may raise suspicion for extracranial meningioma; however, these findings overlap considerably with those of fibrous lesions, epidermoid or dermoid cysts, lipomas, vascular lesions, and soft-tissue sarcomas. This diagnostic difficulty may be even greater when cytologic examination reveals spindle-cell morphology, which can mimic fibrosarcoma, malignant peripheral nerve sheath tumor, or other mesenchymal neoplasms. Accordingly, definitive diagnosis depends on histopathologic and immunohistochemical confirmation.

Histopathologically, extracranial meningiomas closely resemble their intracranial counterparts, showing whorled architecture, psammomatous calcifications, and immunoreactivity for EMA and vimentin. In addition to establishing the diagnosis, histopathologic grading has important prognostic and therapeutic implications. Although most reported extracranial meningiomas are benign and associated with indolent behavior, higher-grade lesions warrant closer attention because recurrence risk may increase according to tumor grade and completeness of resection. In particular, atypical meningiomas classified as WHO grade II are generally considered to have a greater propensity for recurrence than grade I tumors, even though data specific to primary extracranial lesions remain limited. For this reason, postoperative management should be individualized on the basis of histologic grade, residual disease on postoperative imaging, and the feasibility of long-term surveillance.

Complete surgical excision has been the mainstay of treatment in most reported cases and is generally associated with favorable clinical outcomes when gross total resection is achieved [8-10,17,19]. Although recurrence appears to be uncommon, long-term follow-up remains important, particularly in highergrade or incompletely resected tumors. The role of adjuvant radiotherapy remains uncertain and is generally considered on a case-by-case basis, especially for lesions with residual disease, recurrence, or unfavorable histopathologic features. Collectively, the available reports indicate that extracranial meningioma of the temporal region may arise in diverse anatomic sites, often presents as a slowly enlarging painless mass, and is frequently diagnosed only after histopathologic evaluation. Representative reports highlighting these clinicopathologic features and treatment outcomes are summarized in Table 1.

Extracranial meningioma is an uncommon diagnostic consideration in patients presenting with a slowly enlarging temporal mass because both the clinical presentation and radiologic findings are often nonspecific. As shown in previous reports, these lesions usually follow an indolent course and may mimic a broad range of benign and malignant soft-tissue tumors, including fibrous lesions, cystic masses, and sarcomas [3-5,13,15]. Although imaging may demonstrate a skull-adjacent soft-tissue mass with associated bony remodeling or osteolytic change, such findings are not pathognomonic. Instead, the most important radiologic distinction is whether intracranial extension or dural continuity is present, as the absence of these features favors a primary extracranial lesion rather than secondary extracranial spread of an intracranial meningioma [5,7-13,16]. Accordingly, definitive diagnosis still depends on histopathologic and immunohistochemical evaluation.

In the present case, the lesion demonstrated several features characteristic of previously reported temporal-region extracranial meningiomas, including a long-standing painless course, absence of neurologic symptoms, and lack of radiologic evidence of intracranial or dural continuity. CT revealed a well-defined extracranial soft-tissue lesion with irregular destruction of the outer table of the temporal bone, raising suspicion for a muscle-origin neoplasm or soft-tissue sarcoma. Fine-needle aspiration biopsy demonstrated spindle-cell features, which are nonspecific and may overlap with a wide spectrum of benign and malignant soft-tissue tumors. Consequently, preoperative distinction between spindle-cell sarcoma and extracranial meningioma based on cytology alone is challenging.

Definitive diagnosis was achieved through histopathologic examination of the excised specimen, which demonstrated characteristic whorled architecture, multifocal psammomatous calcifications, and diffuse EMA and vimentin positivity, consistent with meningioma. The tumor showed mildly to moderately increased cellularity with occasional prominent nucleoli, without necrosis, and a low Ki-67 proliferation index of approximately 2%, supporting the diagnosis of a WHO grade II meningioma of extracranial origin. These features underscore the limitations of cytologic evaluation and highlight the importance of complete excision for accurate diagnosis in such cases. For clarity, according to the WHO classification, meningiomas are graded into three categories based on histopathologic features. WHO grade I meningiomas are benign tumors characterized by low mitotic activity and the absence of atypical histologic features. WHO grade II (atypical) meningiomas are defined by increased mitotic activity (4–19 mitoses per 10 highpower fields), evidence of brain invasion, or the presence of at least three of the following features: hypercellularity, small cells with a high nuclear-to-cytoplasmic ratio, prominent nucleoli, patternless (sheet-like) growth, or spontaneous necrosis. WHO grade III (anaplastic) meningiomas demonstrate overtly malignant histology, including ≥20 mitoses per 10 high-power fields or frank anaplasia, and are associated with aggressive clinical behavior and a high risk of recurrence.

Complete surgical excision remains the primary treatment modality for extracranial meningiomas [6,13]. Although adjuvant radiotherapy has been proposed for selected cases of WHO grade II meningioma, its role remains controversial, and there is no consensus regarding its routine use following complete resection, particularly in extracranial lesions. Several reviews have emphasized that the decision to administer adjuvant radiotherapy for WHO grade II meningioma should be individualized, taking into account the extent of resection, tumor location, and biological behavior rather than applied routinely [19]. In the present case, adjuvant radiotherapy was not performed because complete gross resection was achieved, postoperative MRI showed no residual disease, the tumor was confined to the extracranial soft tissue without dural or intracranial extension, and the proliferative index was low. Close clinical and radiologic surveillance was therefore considered an appropriate management strategy.

At 3.5 years of follow-up, the patient remains free of recurrence, supporting the individualized treatment decision in this case. Consistent with previous reports, this case provides valuable clinical insight by documenting a rare presentation of primary extracranial meningioma in the temporal region with an unusually long asymptomatic course exceeding 10 years, despite the relatively large tumor size. The purely extracranial location without dural or intracranial involvement and the favorable long-term outcome following complete excision further distinguish this case from previously reported cases. These findings emphasize the importance of considering extracranial meningioma in the differential diagnosis of slowly enlarging temporal masses and demonstrate that tailored surgical management can lead to excellent oncologic and functional outcomes in carefully selected patients [17-20].