Parafalcine lesions in the cancer patient: diagnostic dilemma--meningioma or metastatic lesion?

The authors present two cases that illustrate the difficulty in radiographically distinguishing between meningioma and metastatic lesions in patients with known cancer, especially with a parafalcine tumor location. The first patient with known metastatic prostate cancer had imaging studies suggestive of a parafalcine meningioma, but after surgical resection the lesion was found to be histologically consistent with metastatic disease. Conversely, the second patient was thought to have a metastatic breast cancer lesion in the parafalcine region. This presumptive diagnosis based on imaging findings led the patient to undergo radiosurgery treatment; however, the lesion grew over a several-month course and was eventually resected. The pathological analysis revealed that the tumor was, in fact, a meningioma. Using these cases, as well as an extensive review of the literature, the authors highlight the difficulty in making accurate radiographic diagnosis of dural-based lesions, especially in the parafalcine location, where meningiomas are commonly found but can have multiple entities mimicking their presentation. Caution must be used in managing patients with presumed parafalcine meningiomas or metastatic disease that have no histological diagnosis.