Medical imaging plays a central role in the diagnosis of brain tumors. Early imaging methods – invasive and sometimes dangerous – such as pneumoencephalography and cerebral angiography have been abandoned in favor of non-invasive, high-resolution techniques, especially magnetic resonance imaging (MRI) and computed tomography (CT) scans. Neoplasms will often show as differently colored masses (also referred to as processes) in CT or MRI results.

- Benign brain tumors often show up as hypodense (darker than brain tissue) mass lesions on CT scans. On MRI, they appear either hypodense or isointense (same intensity as brain tissue) on T1-weighted scans, or hyperintense (brighter than brain tissue) on T2-weighted MRI, although the appearance is variable.

- Contrast agent uptake, sometimes in characteristic patterns, can be demonstrated on either CT or MRI scans in most malignant primary and metastatic brain tumors.

- Pressure areas where the brain tissue has been compressed by a tumor also appear hyperintense on T2-weighted scans and might indicate the presence a diffuse neoplasm due to an unclear outline. Swelling around the tumor known as "peritumoral edema" can also show a similar result.

This is because these tumors disrupt the normal functioning of the BBB and lead to an increase in its permeability. However, it is not possible to diagnose high- versus low-grade gliomas based on enhancement pattern alone.

The definitive diagnosis of brain tumor can only be confirmed by histological examination of tumor tissue samples obtained either by means of brain biopsy or open surgery. The histological examination is essential for determining the appropriate treatment and the correct prognosis. This examination, performed by a pathologist, typically has three stages: interoperative examination of fresh tissue, preliminary microscopic examination of prepared tissues, and follow-up examination of prepared tissues after immunohistochemical staining or genetic analysis.

An X-ray computed tomography (CT) or magnetic resonance imaging (MRI) scan is necessary to characterize the extent of these tumors (size, location, consistency). CT will usually show distortion of third and lateral ventricles with displacement of anterior and middle cerebral arteries. Histologic analysis is necessary for grading diagnosis.

In the first stage of diagnosis the doctor will take a history of symptoms and perform a basic neurological exam, including an eye exam and tests of vision, balance, coordination and mental status. The doctor will then require a computerized tomography (CT) scan and magnetic resonance imaging (MRI) of the patient's brain. During a CT scan, x rays of the patient's brain are taken from many different directions. These are then combined by a computer, producing a cross-sectional image of the brain. For an MRI, the patient relaxes in a tunnel-like instrument while the brain is subjected to changes of magnetic field. An image is produced based on the behavior of the brain's water molecules in response to the magnetic fields. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify.

If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy on it. This simply involves the removal of a small amount of tumor tissue, which is then sent to a neuropathologist for examination and grading. The biopsy may take place before surgical removal of the tumor or the sample may be taken during surgery. Grading of the tumor sample is a method of classification that helps the doctor to determine the severity of the astrocytoma and to decide on the best treatment options. The neuropathologist grades the tumor by looking for atypical cells, the growth of new blood vessels, and for indicators of cell division called mitotic figures.

There are no precise guidelines because the exact cause of astrocytoma is not known.

Most of the brain is separated from the blood by the blood-brain barrier (BBB), which exerts a restrictive control as to which substances are allowed to pass. Therefore, many tracers that reach tumors in the body very easily would only reach brain tumors once there is a disruption of the BBB. Thus the disruption of the BBB, which can be detected by MRI and CT, is regarded as the main diagnostic indicator for malignant gliomas, meningiomas, and brain metastases.

Although there is no specific or singular clinical symptom or sign for any brain tumors, the presence of a combination of symptoms and the lack of corresponding clinical indications of infections or other causes can be an indicator to redirect diagnostic investigation towards the possibility of an intracranial neoplasm. Brain tumors have similar characteristics and obstacles when it comes to diagnosis and therapy with tumors located elsewhere in the body. However, they create specific issues that follow closely to the properties of the organ they are in.

The diagnosis will often start by taking a medical history noting medical antecedents, and current symptoms. Clinical and laboratory investigations will serve to exclude infections as the cause of the symptoms. Examinations in this stage may include the eyes, otolaryngological (or ENT) and electrophysiological exams. The use of electroencephalography (EEG) often plays a role in the diagnosis of brain tumors.

Swelling or obstruction of the passage of cerebrospinal fluid (CSF) from the brain may cause (early) signs of increased intracranial pressure which translates clinically into headaches, vomiting, or an altered state of consciousness, and in children changes to the diameter of the skull and bulging of the fontanelles. More complex symptoms such as endocrine dysfunctions should alarm doctors not to exclude brain tumors.

A bilateral temporal visual field defect (due to compression of the optic chiasm) or dilation of the pupil, and the occurrence of either slowly evolving or the sudden onset of focal neurologic symptoms, such as cognitive and behavioral impairment (including impaired judgment, memory loss, lack of recognition, spatial orientation disorders), or emotional changes, hemiparesis, hypoesthesia, aphasia, ataxia, visual field impairment, impaired sense of smell, impaired hearing, facial paralysis, double vision, or more severe symptoms such as tremors, paralysis on one side of the body hemiplegia, or (epileptic) seizures in a patient with a negative history for epilepsy, should raise the possibility of a brain tumor.

Neuroimaging, such as MRI, is the main diagnostic tool for brain stem gliomas. In very rare cases, surgery and biopsy are performed.

Like most tumors in the brain, astroblastoma can be treated through surgery and various forms of therapy. Many publications within the last decade have suggested a noticeable improvement in success rate of patients. With the advancement of cutting-edge technology and novel approaches in stem cells, patients are hopeful that they be happy and healthy through old age.

The following factors influence an oncologist's specific treatment plan:

1. Patient's overall medical history

2. Localization and grade severity of the tumor

3. Age and tolerance to certain medications, procedures, and treatment

4. Predicted progress of recovery

5. Final anticipated outcome of treatment

An X-ray computed tomography (CT) or magnetic resonance imaging (MRI) scan is necessary to characterize the anatomy of this tumor as to size, location, and its heter/homogeneity. However, final diagnosis of this tumor, like most tumors, relies on histopathologic examination (biopsy examination).

The histopathologic grading of oligodendrogliomas is controversial. Currently the most commonly used grading schema is based on year 2007 World Health Organization (WHO) guidelines. An updated classification is in progress. Oligodendrogliomas are generally dichotomized into grade II (low grade) and grade III (high grade) tumors. The designation of grade III oligodendroglioma (high grade) generally subsumes the previous diagnoses of anaplastic or malignant oligodendroglioma.

Unfortunately, the WHO guidelines include subjective criteria in differentiating grade II and grade III tumors including the appreciation of "significant" hypercellularity and pleomorphism in the higher grade lesion. In addition, the presence of low mitotic activity, vascular proliferation and necrosis, including pseudopallisading necrosis are insufficient by themselves to elevate the grade of these tumors. This leads to inevitable interobserver variability in diagnosis by pathologists. The ultimate responsibility for making treatment decisions and interpretation of these diagnoses lies with the oncologist in consultation with the patient and their family.

It has been proposed that WHO guidelines should contain a category for grade IV oligodendrogliomas which essentially appear to be glial neoplasms with overwhelming features of glioblastoma multiforme (GBM) arising from known lower grade oligodendrogliomas or GBM with a significant proportion of oligodendroglial differentiation. The diagnostic utility of this latter category is uncertain as these tumors may behave either like glioblastoma or grade III oligodendrogliomas. As such, this is an exceptionally unusual diagnosis.

The updated WHO guidelines published in 2007 recommends classifying such tumors for the time being as 'glioblastoma with oligodendroglioma component'. It remains to be established whether or not these tumors carry a better prognosis than standard glioblastomas.

If resected, the surgeon will remove as much of this tumor as possible, without disturbing eloquent regions of the brain (speech/motor cortex) and other critical brain structure. Thereafter, treatment may include chemotherapy and radiation therapy of doses and types ranging based upon the patient's needs. Subsequent MRI examination are often necessary to monitor the resection cavity.

Brainstem glioma is an aggressive and dangerous cancer. Without treatment, the life expectancy is typically a few months from the time of diagnosis. With appropriate treatment, 37% survive more than one year, 20% survive 2 years. and 13% survive 3 years.This is not for all brainstem glioma, this statistic reflects DIPG. There are other brainstem gliomas.

Surviving the symptoms of high-grade astroblastoma is not life-threatening, but a significant portion of patients die due to repeated recurrence of tumors as they continue to grow and spread. Unlike conventional low-grade tumors, high-grade tumors associate a plethora of factors when they metastasize to other areas of the body. Therefore, complications frequently occur after surgery is performed since an oncologist cannot efficiently control the tumor in a suitable time-frame. Cases in literature confirm that high-grade patients face up to five or six resection surgeries and "still" experience symptoms post-operatively. The dual-action of chemotherapy and radiotherapy can slow down recurrence when gross total resection is performed multiple times, but there is no guarantee that the tumor will ever be in remission.

It is very difficult to treat glioblastoma due to several complicating factors:

- The tumor cells are very resistant to conventional therapies.

- The brain is susceptible to damage due to conventional therapy.

- The brain has a very limited capacity to repair itself.

- Many drugs cannot cross the blood–brain barrier to act on the tumor.

Treatment of primary brain tumors and brain metastases consists of both symptomatic

and palliative therapies.

Treatment typically consists of radiotherapy and steroids for palliation of symptoms. Radiotherapy may result in minimally extended survival time. Prognosis is very poor, with only 37% of treated patients surviving one year or more. Topotecan has been studied in the treatment of brainstem glioma, otherwise, chemotherapy is probably ineffective, though further study is needed.

A 2014 investigation made a screening of various drugs for anti-glioblastoma activity and identified 22 drugs with potent anti-glioblastoma activity, including the combination of irinotecan and statins.

Computed Tomography (CT) is generally not a recommended modality for diagnosis and evaluation of spinal cord tumors. Evaluation with Magnetic Resonance (MR) most commonly demonstrates a circumscribed solid or mixed solid and cystic mass spanning a long segment of the cord with hypointense T1 signal and hyperintense T2 signal in the solid component. Enhancement patterns are highly variable, ranging from minimal to marked, and may be solid, rim, or nodular. Adjacent cord edema and syringomyelia and peritumoral cysts may be present in addition to reactive scoliosis.

It is nearly impossible to differentiate ganglioglioma from other more common intramedullary neoplasms based on imaging alone. Astrocytoma and ependymoma are more familiar intramedullary tumors which share many similar features to ganglioglioma, including T2 hyperintensity, enhancement, tumoral cysts, and cord edema. Poorly defined margins may be more suggestive of astrocytoma, while a central location in the spinal cord, hemorrhage, and hemosiderin staining are often seen with ependymoma. Hemangioblastoma and paraganglioma are less usual intramedullary tumors, but since they are more frequently encountered than ganglioglioma, they should also be included in the differential diagnosis.

A 2017 meta-analysis compared surgical resection versus biopsy as the initial surgical management option for a person with a low-grade glioma. Results show the evidence is insufficient to make a reliable decision. The relative effectiveness of surgical resection compared to biopsy for people with malignant glioma (high-grade) is unknown.

For high-grade gliomas, a 2003 meta-analysis compared radiotherapy with radiotherapy and chemotherapy. It showed a small but clear improvement from using chemotherapy with radiotherapy.

Temozolomide is effective for treating Glioblastoma Multiforme (GBM) compared to radiotherapy alone. A 2013 meta-analysis showed that Temozolomide prolongs survival and delays progression, but is associated with an increase in side effects such as blood complications, fatigue, and infection. For people with recurrent GBM, when comparing temozolomide with chemotherapy, there may be an improvement in the time-to-progression and the person's quality of life, but no improvement in overall survival, with temozolomide treatment.

A mutational analysis of 23 initial-low grade gliomas and recurrent tumors from the same patients has challenged the benefits and usage of Temozolomide. The study showed that when lower grade brain tumors of patients are removed and patients are further treated with Temozolomide, 6 out of 10 times the recurrent tumors were more aggressive and acquired alternative and more mutations. As one of the last authors, Costello, stated "They had a 20- to 50-fold increase in the number of mutations. A patient who received surgery alone who might have had 50 mutations in the initial tumor and 60 in the recurrence. But patients who received TMZ might have 2,000 mutations in the recurrence." Further, new mutations were verified to carry known signatures of Temozolomide induced mutations. The research suggests that Temozolomide for the treatment of certain brain tumors should be thoroughly thought. Unjudicious usage of Temozolomide might lower the prognosis of the patients further, or increase their burden. Further understanding of the mechanisms of Temozolomide induced mutations and novel combination approaches could be promising.

Definitive treatment for ganglioglioma requires gross total surgical resection, and a good prognosis is generally expected when this is achieved. However, indistinct tumor margins and the desire to preserve normal spinal cord tissue, motor and sensory function may preclude complete resection of tumor. According to a series by Lang et al., reviewing several patients with resected spinal cord ganglioglioma, the 5- and 10-year survival rates after total resection were 89% and 83%, respectively. In that study, patients with spinal cord ganglioglioma had a 3.5-fold higher relative risk of tumor recurrence compared to patients with supratentorial ganglioglioma. It has been recognized that postoperative results correlate closely with preoperative neurological status as well as the ability to achieve complete resection.

With the exception of WHO grade III anaplastic ganglioglioma, radiation therapy is generally regarded to have no role in the treatment of ganglioglioma. In fact, radiation therapy may induce malignant transformation of a recurrent ganglioglioma several years later. Adjuvant chemotherapy is also typically reserved for anaplastic ganglioglioma, but has been used anecdotally in partially resected low grade spinal cord gangliogliomas which show evidence of disease progression.

Gliomas are rarely curable. The prognosis for patients with high-grade gliomas is generally poor, and is especially so for older patients. Of 10,000 Americans diagnosed each year with malignant gliomas, about half are alive one year after diagnosis, and 25% after two years. Those with anaplastic astrocytoma survive about three years. Glioblastoma multiforme has a worse prognosis with less than a 12-month average survival after diagnosis, though this has extended to 14 months with more recent treatments.

Oligodendrogliomas cannot currently be differentiated from other brain lesions solely by their clinical or radiographic appearance. As such, a brain biopsy is the only method of definitive diagnosis. Oligodendrogliomas recapitulate the appearance of the normal resident oligodendroglia of the brain. (Their name derives from the Greek roots 'oligo' meaning " few" and 'dendro' meaning "trees".) They are generally composed of cells with small to slightly enlarged round nuclei with dark, compact nuclei and a small amount of eosinophilic cytoplasm. They are often referred to as "fried egg" cells due to their histologic appearance. They appear as a monotonous population of mildly enlarged round cells infiltrating normal brain parenchyma and producing vague nodules. Although the tumor may appear to be vaguely circumscribed, it is by definition a diffusely infiltrating tumor.

Classically they tend to have a vasculature of finely branching capillaries that may take on a "chicken wire" appearance. When invading grey matter structures such as cortex, the neoplastic oligodendrocytes tend to cluster around neurons exhibiting a phenomenon referred to as "perineuronal satellitosis". Oligodendrogliomas may invade preferentially around vessels or under the pial surface of the brain.

Oligodendrogliomas must be differentiated from the more common astrocytoma. Non-classical variants and combined tumors of both oligodendroglioma and astrocytoma differentiation are seen, making this distinction controversial between different neuropathology groups. In the US, in general, neuropathologists trained on the West Coast are more liberal in the diagnosis of oligodendrogliomas than either East Coast or Midwest trained neuropathologists who render the diagnosis of oligodendroglioma for only classic variants. Molecular diagnostics may make this differentiation obsolete in the future.

Other glial and glioneuronal tumors with which they are often confused due to their monotonous round cell appearance include pilocytic astrocytoma, central neurocytoma, the so-called dysembryoplastic neuroepithelial tumor, or occasionally ependymoma.

The standard treatment for DIPG is 6 weeks of radiation therapy, which often dramatically improves symptoms. However, symptoms usually recur after 6 to 9 months and progress rapidly.

Surgery to attempt tumour removal is usually not possible or advisable for DIPG. By nature, these tumours invade diffusely throughout the brain stem, growing between normal nerve cells. Aggressive surgery would cause severe damage to neural structures vital for arm and leg movement, eye movement, swallowing, breathing, and even consciousness.

A neurosurgically performed brain-stem biopsy for immunotyping of diffuse intrinsic pontine glioma has served a limited recent role in experimental clinical studies and treatment trials. This however is not the current standard of care as it presents considerable risk given the biopsy location, and thus is appropriately performed in the context of participation in an ongoing clinical treatment trial.

Pontine biopsy is in no way a therapeutic or curative surgery, and the risks (potentially catastrophic and fatal) are only outweighed when the diagnosis is uncertain (extremely unusual) or the patient is enrolled in an approved clinical trial.

An MRI is better than a CT scan when a brainstem tumor is in the differential diagnosis.

Urine catecholamine level can be elevated in pre-clinical neuroblastoma. Screening asymptomatic infants at three weeks, six months, and one year has been performed in Japan, Canada, Austria and Germany since the 1980s. Japan began screening six-month-olds for neuroblastoma via analysis of the levels of homovanillic acid and vanilmandelic acid in 1984. Screening was halted in 2004 after studies in Canada and Germany showed no reduction in deaths due to neuroblastoma, but rather caused an increase in diagnoses that would have disappeared without treatment, subjecting those infants to unnecessary surgery and chemotherapy.

Magnetic resonance imaging (MRI) and computed tomography (CT) brain scans can be used to identify these tumors.

The primary diagnosis is made with a computed tomography scan (CT scan). On a scan, hemangioblastoma shows as a well-defined, low attenuation region in the posterior fossa with an enhancing nodule on the wall. Sometimes multiple lesions are present.