I’ve gotten a few requests through Twitter for posts on neuropathology. Great idea! It’s a big subject – so we’ll break it down into manageable chunks. We’ll start with a short introduction to brain tumors, followed by separate discussions of each major tumor.
Brain tumors can be primary or secondary. Secondary tumors may occur by metastasis from distant tumors (most commonly lung or breast carcinomas) or by expansion of a nearby tumor (such as a craniopharyngioma).
Primary tumors arise directly from cells of the nervous system or its coverings. They can be broadly grouped into 4 main categories.
Gliomas This is the most common group of primary brain tumors. Gliomas arise, not surprisingly, from glial cells (astrocytes, oligodendrocytes, or ependymal cells). These tumors are often fatal because their location within the brain – and their infiltrating nature – prevent curative resection. Types of gliomas include astrocytomas (the most common of the group), oligodendrogliomas, ependymomas, and glioblastomas. Glioblastomas are part of the spectrum of astrocytoma; they are the most malignant of all.
Tumors of neuronal lineage These include gangliomas (benign tumors which contain mature-appearing neurons), and medulloblastomas (which contain poorly-differentiated neuroectodermal cells). Medulloblastomas are highly malignant tumors of the cerebellum that usually occur in children.
Meningiomas Meningiomas are usually benign, and are most common in adults. They arise from cells of the arachnoid membrane, and are usually attached to the dura. They may compress the brain, but are usually easily separated from it. If surgically accessible, meningiomas are usually cured by resection.
Nerve sheath tumors These tumors arise from cells of the peripheral nerve (Schwann cells, perineurial cells, and fibroblasts). The two main types are Schwannomas (intracranially, these are most common at the cerebellopontine angle attached to the vestibular branch of the eighth nerve, where they are referred to as “acoustic neuromas”) and neurofibromas (which are often more peripheral, and may occur in the skin). Nerve sheath tumors are usually benign, but may compress nerves, leading to permanent damage.