Meningiomas have been implicated as the most common primary intracranial tumor to contain tumor-to-tumor metastasis. In the following two case reports, we describe cases of adenocarcinoma and breast carcinoma that metastasized into an intracranial meningioma. The first patient was a 64-year-old man presenting to the emergency department with seizures and loss of consciousness. After a left frontal mass resection, pathology reported a heterogeneous mass consisting of a meningioma and a metastatic adenocarcinoma component. The second patient was a 63-year-old woman presenting with significant vision problems and unstable gait. After a right frontal mass resection, pathology reported a heterogeneous mass consisting of a meningioma and a metastatic breast carcinoma component. Possible explanations for the development of the tumor-to-tumor metastasis are described.
Despite the innate immune responses from resident microglia, astrocytes and infiltrating T cells, the CNS is susceptible to many different types of primary neoplasms and metastases . The Central Brain Tumor Registry of the United States emphasized the rarity of CNS tumors by suggesting an incidence of 22.36 cases per 100,000. Of CNS tumors, aggressive non-neural metastases are the largest contributors with an incidence of 10 cases per 100,000 [2–4]. On the other hand, meningiomas are the most common intracranial tumors with an incidence of 7.61 cases per 100,000 [5,6].