Thymic Carcinoma with Brain Metastasis Mimicking Meningioma

Thymic carcinoma is a rare malignancy, which differs from thymoma in that it displays histopathologically malignant features, extensive local invasion, and a substantial potential for metastasis, predominantly to the liver and kidney and rarely to the central nervous system. Most of cerebral metastases are the intraaxial tumor, whereas extraaxial masses mimicking meningioma are extremely rare. A 32-year-old woman who had been treated for thymic carcinoma with multiple bone metastasis including spine and ribs was referred to the neurosurgery department with a diagnosis of right temporal extraaxial mass. Magnetic resonance imaging (MRI) revealed an extraaxial tumor with hemorrhage along the medial margin of tumor. A craniotomy was performed to remove the mass that was located extraaxially. Histopathological and immunohistochemical examination revealed undifferentiated thymic carcinoma with neuroendocrine differentiation. The patient recovered from the preoperative deficits, and local irradiation of 50Gy was performed. This paper will examine briefly the radiolographic and pathologic characteristics of this unusual lesion. Although extraaxial thymic carcinomas are rare, they should be considered in the radiographic differential diagnosis of dural-based lesions, especially for patients with history of thymic lesions.