Glioblastoma refers to a group of highly malignant primary brain tumors that share histopathologic features, meaning they kind of look the same under a microscope. Our understanding of glioblastomas is incomplete. So we're still learning ways in which we can more adequately classify and define these tumors in a way that both informs our understanding of the nature of the disease and informs the way that we can treat patients with glioblastoma. Glioblastoma is far and away the most common primary brain malignancy. To be clear, that does not include metastases, which is not a primary brain tumor. And that doesn't include meningiomas, which is not a malignant tumor most of the time. Glioblastoma is still relatively rare, affecting about seven per a hundred thousand people. It affects men slightly more commonly than women and its incidence occurs typically later in life, peaking in the eighth decade.