Metastases to Meningiomas: A Comprehensive Literature Review Including Mediating Proteins

SIMPLE SUMMARY: Metastasis from recognized, or occult, malignancies to a co-existing meningioma can present diagnostic challenges. This is, in part, do to the potential histological similarity of the metastasis to the recipient meningioma tissue. Moreover, the discovery of the metastases, particularly from an occult tumor, has important therapeutic implications for managing these scenarios. The review was undertaken to determine the types of neoplasms that spread to meningiomas and identify what histologic subtypes of meningiomas that are at greatest risk of receiving metastases. The histologic challenges of identifying small metastases in meningiomas are discussed. The molecules and mechanisms by which they facilitate this tumor-to-tumor spread are discussed. ABSTRACT: Approximately 5–15% of solid tumors metastasizing to the central nervous system metastasize to the leptomeninges. Less common, is metastasis to leptomeningeal meningiomas. These are primarily carcinomas of the breast and lung. Awareness of this phenomenon is critical to the evaluation of meningiomas, especially since the metastases may be the first indication of an occult tumor elsewhere in the body. Lack of clear demarcation between the metastasis and meningioma parenchyma, as well as histological features similar to the meningioma, may hinder recognition. The mechanisms underlying metastases anchoring and spread along the leptomeninges are not established. However, several cell adhesion molecules are thought to contribute to this phenomenon. E cadherin is a cell adhesion molecule present in meningioma cells. Binding to endothelium by adhesion molecules such as ICAM, B1 integrin, P-selectin, PECAM-1, CXCL12 and SDF-1 have also been proposed as part of the mechanisms underlying breast carcinoma metastases. In addition, the leptomeninges and meningiomas express mesothelin that acts as an anchoring protein coupling with mucin-16. Consequently, metastatic tumor cell mucin and mesothelin may also facilitate the anchoring of metastases to meningiomas.