Cancer metastases to meningioma: apropos two cases.

Tumour-to-tumour metastasis (TTTM) is the uncommon phenomenon in the systemic and central nervous system neoplasia. We report on two new cases of metastases to meningioma. The first case concerned a patient with renal cancer and synchronous asymptomatic meningioma followed up radiologically. In the fifth year of observation, he developed acute neurological symptoms. Neuroimaging showed meningioma enlargement with irregular surrounding oedema. On gross exam, the tumour had two different components, which histopathologically comprised atypical meningioma and renal cancer deposits. The patient's postoperative course was complicated with a subdural hematoma. The second TTTM case concerned a patient with a two-year history of colorectal cancer treatment with recent severe headaches. Radiologically the temporal lobe metastatic focus was detected. During cerebral metastasectomy, small meningeal incidentaloma was resected, histologically being meningioma with adenocarcinoma metastasis. Tumour metastasis to meningioma can be the only one or one of the places of cancer dissemination. TTTM can cause postoperative complications. Our cases prove the importance of the careful sampling of tumours and necessity of immunohistochemistry in differential diagnosis between meningioma subtypes and metastatic focus.