Primary CNS Tumors^[3]

Primary CNS tumors originate within the brain or spinal cord. They can be benign (non-cancerous) or malignant (cancerous). Some common types of primary CNS tumors include:

• Gliomas: Tumors arising from glial cells, which support and protect neurons. Subtypes include astrocytomas, oligodendrogliomas, and glioblastomas^[2].

• Meningiomas: Tumors that develop in the meninges, the protective membranes covering the brain and spinal cord. These are typically benign and more common in adults^[4].

• Medulloblastomas: Malignant tumors that commonly occur in the cerebellum, most often in children^[4].

• Ependymomas: Tumors that arise from the ependymal cells lining the ventricles of the brain and the central canal of the spinal cord^[4].

Primary PNS Tumors

Primary PNS tumors originate in the peripheral nerves and nerve sheaths. These tumors are often benign but can sometimes be malignant. Common types of primary PNS tumors include:

• Schwannomas: Tumors arising from Schwann cells, which produce the myelin sheath surrounding peripheral nerves. A common subtype is the vestibular schwannoma (acoustic neuroma)^[5].

• Neurofibromas: Benign tumors that grow on nerves, commonly associated with neurofibromatosis type 1 (NF1)^[2].

• Malignant Peripheral Nerve Sheath Tumors (MPNST): Rare but aggressive cancers that arise from peripheral nerves or nerve sheath cells^[6].

Secondary (Metastatic) CNS Tumors

Secondary CNS tumors, or metastatic tumors, occur when cancer cells spread to the brain or spinal cord from a primary tumor in another part of the body. These tumors are more common than primary CNS tumors in adults and often originate from cancers such as: ^[7]

• Lung Cancer
• Breast Cancer
• Melanoma
• Kidney Cancer
• Colon Cancer

Clinical Evaluation

Diagnosing nervous system neoplasms typically begins with a comprehensive medical history and neurological examination. The goal of the evaluation is to identify any neurological changes that may suggest the presence of a tumor. The assessment considers factors such as the nature, progression, and duration of the patient's symptoms, as well as any relevant medical history.^[8]

Because nervous system neoplasms can have a wide range of presentations, clinical evaluation is often followed by neuroimaging to confirm or rule out the presence of a tumor. Further testing, such as a biopsy, may be necessary to determine the tumor type and grade.^[2][8]

Advances in Diagnostic Methods

Advances in imaging technologies, molecular diagnostics, and targeted therapies have significantly improved the accuracy of diagnosis and the effectiveness of treatment.^[9][10][3].

Neuroimaging

Magnetic Resonance Imaging (MRI) with contrast is the primary imaging modality for diagnosing brain and spinal cord tumors due to its high-resolution visualization of soft tissues. MRI helps identify the tumor's location, size, and potential impact on surrounding structures. In emergency situations or when MRI is contraindicated, Computed Tomography (CT) is used as an alternative.^[11]

Advanced Imaging Techniques

Additional imaging techniques can provide further insights when standard MRI or CT findings are inconclusive: ^[2]

• Magnetic Resonance Spectroscopy (MRS) analyzes the chemical composition of brain tissue to differentiate tumors from non-neoplastic conditions such as infections or demyelinating diseases.
• Positron Emission Tomography (PET) assesses metabolic activity and can distinguish between tumor recurrence and treatment-related changes.
• Diffusion Tensor Imaging (DTI) maps white matter tracts and helps plan surgeries to avoid critical brain regions.

Biopsy and Pathological Analysis

A definitive diagnosis often requires a tissue biopsy. The biopsy can be performed through an open surgical procedure or a minimally invasive stereotactic technique.^[12] Histopathological examination determines the tumor type, grade, and molecular characteristics, which are critical for guiding treatment decisions.^[13]

Advances in molecular diagnostics allow for the identification of genetic and molecular markers, improving the precision of tumor classification and enabling targeted therapies.^[14]

Lumbar Puncture

In some cases, a lumbar puncture (spinal tap) may be performed to analyze cerebrospinal fluid (CSF). This can help detect tumor cells, especially in cases of suspected leptomeningeal metastasis or primary CNS lymphoma. The presence of tumor markers or abnormal cells in the CSF can provide diagnostic information that complements imaging and biopsy findings.^[2]

Gliomas

Gliomas, tumors originating from glial cells, are the most common malignant primary brain tumors, accounting for approximately 81% of malignant brain tumors and 26% of all brain and CNS tumors^[15] . Gliomas arise from different types of glial cells:

• Astrocytes – resulting in astrocytomas
• Oligodendrocytes – resulting in oligodendrogliomas
• Ependymal cells – resulting in ependymomas

Glioblastomas, the most aggressive form of glioma, make up approximately 47.7% of all gliomas^[15]. The incidence rate of glioblastomas is 3.23 per 100,000 people^[9]. The 5-year survival rate for glioblastoma is only 6.8%^[9].

Meningiomas

Meningiomas, which develop in the meninges, are common primary brain tumors, representing approximately 37% of all brain tumors^[15]. The incidence rate for meningiomas is 9.51 per 100,000 people^[9]. Unlike gliomas, more than 98% of meningiomas are nonmalignant^[15]. The 5-year survival rate for nonmalignant meningiomas is approximately 91%^[9].

Pediatric Brain Tumors

In children aged 0–14 years, the most common brain tumors are: ^[15]

• Pilocytic astrocytomas – 17.5%
• Embryonal tumors – 15.7%
• Malignant gliomas – 25.7%

The overall incidence rate of brain tumors in children is 6.2 per 100,000^[9].

The distribution and behavior of nervous system neoplasms differ significantly between adults and children. Gliomas are more frequent and aggressive in adults, while certain benign tumors like pilocytic astrocytomas are more common in children. Notably, adults are more likely to develop secondary (metastatic) tumors that spread to the nervous system from cancers originating in other parts of the body^[1].

Demographic Trends

Brain tumor incidence varies by age, sex, and race. Overall, brain and CNS tumors are more common in females due to the higher prevalence of meningiomas^[9]. However, malignant tumors like glioblastomas are more frequently diagnosed in males^[9].