Intracranial meningioma masquerading as a primary pleuropulmonary tumor.

Extracranial metastasis was found in an intracranial meningioma with low proliferative potential before the detection of the primary tumor. Pleuropulmonary tumors were incidentally detected on chest X-ray in an asymptomatic 25 year old female. Excised tumors of the right pleura and lung showed histological features similar to meningotheliomatous meningioma, which led to the discovery and excision of the intracranial tumor. Both tumors showed the same histologic pattern: meningotheliomatous meningioma with low mitotic activity. The proliferative component, determined by the monoclonal antibody Ki-67, was further evaluated in the primary tumor and the metastases of the present case, as well as in 12 other intracranial meningiomas. Ki-67 positive ratios at the primary and metastatic sites of the present cases were 1.2 and 1.1%, respectively, which is as low as other benign meningiomas, and this suggests that factors other than the proliferative potential is responsible for extracranial metastasis of meningioma.