Sphenoid Temporal Meningioma With Granular Cell Features and Extracranial Infratemporal Extension

Meningiomas usually arise from arachnoid cap cells and present as intracranial, dural-based lesions. Extracranial extension into the temporalis muscle, infratemporal fossa, orbit, and skull base foramina is uncommon and can mimic primary soft-tissue or peripheral nerve sheath tumors. We report a 54-year-old female who presented with a slowly progressive right-sided facial and temporal swelling over two years, associated with intermittent pain and mild proptosis but no focal neurological deficit. Computed tomography demonstrated a small extra-axial minimally enhancing right anterior temporal lesion with calcific foci, marked hyperostosis of the right frontal bone, lateral orbital wall, greater wing of the sphenoid, and squamous temporal bone, and enhancing bulkiness of the right temporalis muscle extending into the infratemporal fossa. She underwent right temporal craniotomy with excision of the temporal and infratemporal soft-tissue component, resection of hyperostotic bone, decompression of the orbital wall, and titanium mesh cranioplasty. Histopathology showed an ill-defined tumor infiltrating soft tissue and skeletal muscle, composed of nests and sheets of round-to-polygonal cells with abundant eosinophilic granular cytoplasm, bland round-to-oval nuclei, inconspicuous nucleoli, focal whorling, and psammoma body-like calcifications. Immunohistochemistry showed diffuse S100 positivity, focal epithelial membrane antigen positivity, progesterone receptor positivity, focal CD68 positivity, STAT6 negativity, and a Ki-67 proliferation index below 1%, favoring meningioma with granular cell features and CNS WHO grade 1. This case highlights the importance of integrating skull base imaging, operative findings, and immunohistochemistry when evaluating lateral skull base masses with hyperostosis and extracranial soft-tissue extension.