Pathology

Grossly, meningiomas are firm well-circumscribed tumors, appearing smooth or lobulated, gray-white, tan, or pink. Microscopically, four histologic patterns are described: (1) syncitial which is most common; (2) fibroblastic; (3) transitional, and (4) angioblastic. The angioblastic pattern has the greatest predilection for locally aggressive behaviour, malignancy, and the worse prognosis.59 Psammoma bodies and a whorled parenchymal pattern can be found in all types. Mitoses are usually rare or absent.61-64

Jugular foramen meningiomas may represent (1) the extracranial extension of a primary intracranial meningioma tumor; (2) a tumor arising in the jugular foramen; (3) a tumor arising from the arachnoidal cell clusters within the trunk or perineural sheath of one of the lower cranial nerves within or near the jugular foramen; or (4) a metastasis to cervical lymph nodes from a primary intracranial meningioma.59,65

Meningiomas spread along preformed bony channels. The most common pathway for extracranial meningioma to extend beyond the confines of the skull is through the jugular foramen into the parapharyngeal space.59 The vascular spongiotic spaces may be diffusely infiltrated by tumor cells. Intracranial meningiomas that develop an extracranial extension via the jugular foramen assume an hourglass or dumbbell tumor configuration. The adjacent bone may show evidence of the classic reactive sclerosis and hyperostosis. In contrast, meningiomas originating from within the jugular foramen follow the direction of least resistance as they increase in size. They extend extracranially into the parapha-ryngeal space and neck, without entering the posterior cranial fossa.59 Origin within the foramen of the skull base is evident by the extracranial parapharygeal location of these tumors, their firm attachment to the skull base at the jugular foramen, and the absence of any tumor tissue within the posterior cranial fossa.59

Meningiomas are usually solitary, slow-growing tumors that compress, rather than invade, the lower cranial nerves and the jugular vein within the jugular foramen. However, they may be multiple and, in rare cases, may invade vessels and nerves. Tumor extension along the lumen of the internal jugular vein has been reported, but is not characteristic.66 In patients with extracranial meningiomas or multiple meningiomas or who are younger than 30 years of age, the central form of neurofibromatosis should be suspected.67

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