What is a typical characteristic of a meningioma?

A meningioma is primarily characterized by its encapsulated nature. This means that it typically forms a well-defined boundary that is distinct from the surrounding brain tissue. Meningiomas originate from the meninges, the protective layers surrounding the brain and spinal cord, and as they grow, they do so in a way that allows them to maintain this clear separation from adjacent structures. This encapsulation not only helps in the surgical removal of the tumor, as it can often be excised while preserving surrounding brain tissue, but also aids in radiological identification, as meningiomas are usually seen as distinct masses on imaging studies.

In contrast, tumors that are infiltrating tend to invade neighboring tissues, making surgical removal more complicated. Rapidly growing tumors typically indicate a more aggressive type of cancer, which is not characteristic of most meningiomas as they often have a slower growth rate. Additionally, meningiomas are generally primary tumors, meaning they are not metastatic; they originate from cells in the meninges rather than from other areas of the body. Therefore, being encapsulated is a defining feature of meningiomas that supports their identification and management in clinical contexts.