Tumor-to-tumor metastasis to the central nervous system.

Tumor-to-tumor metastasis is a well-recognized phenomenon. Meningioma is the most common intracranial host tumor, with the breast and lung being the most common primary sites. We report herein two such cases of metastasis from pulmonary adenocarcinoma and malignant melanoma (MM) of vulva, respectively. Case 1: a 69-year-old female smoker who had a history of right upper lobectomy of lung for adenocarcinoma presented with a headache and altered mental status, and was found to have a left temporal contrast-enhancing mass with massive surrounding edema on MRI. The resection specimen revealed foci of metastatic adenocarcinoma within a microcystic meningioma. Case 2: a 75-year-old woman with a history of radical vulvectomy for MM died of widespread systemic metastasis of MM. At autopsy, a 2.5 x 2 x 2 cm firm nodule attached to the falx was incidentally found, with focal black discoloration at the periphery of the mass. Histologic examination showed a fibroblastic meningioma with a focus of metastatic MM. Case 1 is the first case report describing a microcystic variant of meningioma harboring metastatic carcinoma. Although MM is one of the most common metastatic brain tumors, MM-to-meningioma metastasis is reportedly extremely rare, but can occur.