Extracranial Spread of Meningiomas: Molecular Determinants, Diagnostic Pathways, and Lessons From Three Thoracic Metastases.

Meningiomas are the most common primary intracranial neoplasms of all brain tumors. Although the majority are benign, a subset displays aggressive behavior characterized by recurrence, anaplastic transformation, or, rarely, extracranial metastasis. Lung parenchyma represents the most frequent site of spread, followed by mediastinal and pleural involvement. Despite recent advances in molecular characterization, predicting metastatic potential remains challenging. We report three cases of meningiomas with thoracic metastases illustrating distinct biological trajectories. Case 1 involved a 33-year-old woman with a germline BAP1 mutation and recurrent cerebellopontine angle meningioma (WHO grade 1). After multiple resections and radiotherapy, surveillance imaging revealed pulmonary and hilar lesions. Both EBUS-TBNA and percutaneous lung biopsy confirmed a metastatic meningioma (EMA+, SSTR2+, PR rare+, BAP1 loss). Case 2 describes a 45-year-old man with a de novo anaplastic meningioma (WHO grade 3) who later developed multiple bilateral pulmonary nodules confirmed via robotic-assisted bronchoscopy (EMA+, SSTR2+, CAM5.2-). Case 3 details a 79-year-old man with a recurrent spheno-orbital anaplastic meningioma who developed bilateral pulmonary metastases diagnosed by Ion robotic bronchoscopy and confirmed by neuropathology (SSTR2+, EMA focal+, PR+). Meningioma metastasis remains exceedingly rare, but risk increases with higher grade, recurrence, and molecular alterations such as BAP1 loss or NF2 inactivation. Latency varies from months in anaplastic cases to decades in low-grade tumors. Minimally invasive techniques, including EBUS-TBNA and robotic bronchoscopy, provide accurate and safe diagnostic confirmation, especially when thoracic disease is suspected. Thoracic metastases from meningioma demonstrate diverse clinical courses independent of histologic grade. Molecular profiling, particularly BAP1 and NF2 status, may refine risk assessment and justify risk-adapted surveillance incorporating chest imaging or PET/CT. Treatment is largely palliative, with local resection or radiotherapy offering control in selected cases. Continued integration of molecular diagnostics and modern bronchoscopic technologies may improve recognition and management of these rare metastatic events.