How is oligodendroglioma serious?

How is oligodendroglioma serious? s oligodendroglioma highly malignant? Oligodendroglioma accounts for about 4% of intracranial gliomas and 3% to 12% of neuroepithelial tumors.

• It is more common in adults, usually around middle age, and the average age of onset is 38 to 45 years old, with slightly more men.
• More than 80% of oligodendrogliomas are located in the white matter of the cerebral hemisphere. The frontal lobe is the most common, accounting for about half, followed by the parietal lobe, temporal lobe, lateral ventricle and posterior fossa.
• The proportion of anaplastic oligodendroglioma in oligodendroglioma is quite different in the statistics of different pathological centers.

Pathological characteristics

· Oligodendroglioma is WHO grade II

· Anaplastic oligodendroglioma is WHO grade III

· Originated from the malignant transformation of mature oligodendroglial cells or glial precursor cells

· According to the 2016 World Health Organization’s central nervous system tumor genetic classification: IDH mutant, ATRX wild type and 1p/19q co-deletion

· Oligodendrogliomas are mostly located in the white matter, and those located in the cortex can be seen. The tumors are grayish-red in appearance, soft in texture, and often have a wide range of infiltration. They tend to infiltrate deep midline structures, such as invading the lateral ventricle wall and transparent septum. Union with thalamus. 40% of tumors have calcified masses, and 20% have cystic changes. The boundary with the brain tissue is clear, and sometimes a false capsule can be seen. Some tumors have mucinous changes, which aggregate into jelly-like substances. Because the nucleus of the tumor cells is round and the cytoplasmic boundary is clear and uniform, it appears as a “fried egg” appearance under a light microscope

· Anaplastic oligodendroglioma also has obvious calcification. The histological morphology of tumors in high-malignant tumors is similar to glioblastoma, and the histological morphology of tumors in high-malignant tumors is similar to that of glioblastoma. The fundamental difference of glioma is that tumor cells are extremely abundant, morphologically diverse, and the ratio of nucleus to cytoplasm is increased. Mitosis is more common, and very few extracranial metastases can occur, mainly bones, lymph nodes, and lungs.

Causes

Molecular biology studies have shown that the occurrence of oligodendroglial tumors is related to the loss of heterozygosity on the long arm of chromosome 19 (19q). There are data showing that individual cases have been exposed to radiation for other reasons, but this only accounts for a very small part of oligodendrocyte tumors. Chemical carcinogens such as ethylnitrosourea and methylnitrosourea can induce the occurrence of rat CNS tumors. Among them, oligodendroglioma and oligoastrocytoma are the most common, but it is not yet certain that these substances are The cause of glioma. Some studies have proved that there are virus gene sequences and proteins (SV40, BK, JC virus) in oligodendroglioma, but some people have not detected the virus sequence. Therefore, the cause of the virus is currently uncertain.

Clinical manifestations

· The course of the disease is mostly gradual development, but may suddenly worsen.

· Most patients with oligodendroglioma grow slowly and have a long course of disease. The average time from symptom onset to consultation is 2 to 3 years. It has been reported that the course of disease is 2.4 to 4.1 years, and the longest is 31 years.

· Epilepsy is the most common symptom. It is the most common among neuroepithelial tumors. Epilepsy is often the first symptom. It is seen in 50% of patients and 85% of patients have seizures. Patients who start with epilepsy generally have a longer course of disease.

· Some patients were misdiagnosed as primary epilepsy and treated for many years, and the tumor was not discovered until symptoms of increased intracranial pressure appeared.

· According to statistics, 10% of intracranial tumors that can cause epilepsy are oligodendroglioma. In addition to epilepsy, patients still have headaches (80%), mental disorders (50%), and limb weakness (45%).

· Psychiatric symptoms are common in patients with frontal oligodendroglioma, especially those with extensive infiltration and expansion along the corpus callosum to the contralateral frontal lobe. Neurological symptoms, mainly emotional abnormalities and dementia.

· Increased intracranial pressure is seen in about half of patients, and generally appears late. In addition to headaches and vomiting, visual impairment and optic disc edema account for about 1/3 of patients.

· Tumor invading the motor and sensory areas can correspondingly produce hemiplegia, hemisensory disturbance, and motor or sensory aphasia. Most patients with anaplastic oligodendroglioma have a short course of disease, with obvious symptoms of intracranial hypertension and focal nervous system symptoms.

Treatment

The treatment is based on surgical resection, and the principle of surgery is to remove as many tumors as possible. However, because the tumor invades the midline structure or the wall of the lateral ventricle, it often affects the scope of surgical resection. Many reports have reported a gross gross tumor resection rate of about 30%. It has been reported that the more thorough the tumor is removed, the lower the surgical mortality rate. If the tumor is confined to one frontal lobe, temporal lobe or occipital lobe, surgical resection is an ideal method. Patients with more complete resection often get better results after surgery.

There is no unified understanding of postoperative radiotherapy and chemotherapy for oligodendroglioma. However, for patients with rapidly growing or recurring oligodendroglioma, postoperative radiotherapy and chemotherapy are recommended. In recent years, studies have shown that oligodendroglioma is a chemotherapy-sensitive tumor that responds well to procarbazine (procarbazine), lomustine and vincristine series therapy (PCV).

The treatment of anaplastic oligodendroglioma is still based on total resection of the tumor, and postoperative radiotherapy is necessary. Chemotherapy is effective for anaplastic oligodendroglioma, and PCV combination therapy is often used.

Prognosis

The prognosis of patients with oligodendroglioma is better than that of patients with astrocytoma. Long-term survival may be achieved even without radiotherapy or chemotherapy. For patients with subtotal tumor resection and postoperative radiotherapy, the 5-year survival rate can reach 85%, the 10-year survival rate is 55%, and the average survival time is 8.0 years. Individual reports have reached 40 years, with an average survival of 3.3 years after only partial resection (including biopsy and decompression). However, the data of each family are quite different.The longer median survival time is 15 years, and the shorter one is 3.5 years, which may be due to the difference in diagnostic criteria (hence the ratio of 1p/19 missing cases) and treatment measures. Caused by.

Surgery can significantly alleviate headaches and other symptoms, but has limited control of epilepsy. Many patients still have seizures after surgery. However, despite the comprehensive treatment measures such as surgery, radiotherapy, and chemotherapy, almost every case has the possibility of recurrence. Recurrent tumors can become malignant. 50% to 70% of recurrent oligodendrogliomas will become anaplastic, and 15% of recurrent tumors will become glioblastoma multiforme. The prognosis of recurrent tumors is often poor. It can be operated again to prolong life, and postoperative radiotherapy has a certain effect, and the 5-year and 10-year survival rates can reach 52% and 32%.

The prognosis of anaplastic oligodendroglioma is poor, with a 5-year survival rate of 43%. The average survival time is 3.75 to 4.5 years, and the survival time of the tumor is longer in the frontal lobe. The average survival time of those with high malignancy is only 1.4 years.

Prognostic factors

[Clinical factors related to better prognosis]

· The patient was young at the time of surgery

· The tumor is located in the frontal lobe

· Postoperative Karnofsky score

· Neuroimaging without contrast enhancement

· Gross tumor cut

[Factors related to poor histological prognosis]

· Necrotic mitotic figures, high cell density, nuclear atypia, cell pleomorphism and microvascular proliferation (see anaplastic oligodendroglioma)

· The appearance of small obese cells and glial fibrous oligodendrocytes has nothing to do with survival time.

【Hyperplasia】

· A large number of studies have evaluated the significance of the Ki67 (MIB-1) index in judging the prognosis. Usually, a high proliferation rate (>3%~5%) is significantly associated with a poor prognosis.

· A study of 32 cases of WHO grade II oligodendroglioma showed that Ki-67 markers higher than 3% have a bad prognosis.

· Another 89 cases of oligodendroglioma study showed that the 5-year survival rate of MIB-1 marker index <5% was 83%, and MIB-1 positive cells>5%, the 5-year survival rate was only 24% of cases.

· Similar reports divide patients into two groups with 5% MIB-1 positive cells as the boundary. The survival rate of patients is significantly different.

· The value of evaluating tumor cell proliferation rate has nothing to do with the influence of patient age, tumor location and histological grade.

【Genetics】

· Some retrospective studies have shown that WHO grade II oligodendroglioma with combined deletion of 1p or 119q grows more slowly, and patients survive longer, usually more than 10 years. Therefore, the detection of chromosomes 1p and 19q may help to judge the prognosis.

· But the actual efficacy evaluation is more difficult than anaplastic oligodendroglioma, because WHO grade II oligodendroglioma is not very sensitive to radiotherapy and requires long-term follow-up.

· However, a small-scale study of temozolomide in the treatment of low-grade oligodendroglioma found that 1p deletion is related to the tumor’s radiotherapy response.

· The above findings suggest that the prolonged survival time of patients may be caused by the slow growth of the tumor itself and the sensitivity to treatment.

Related references:

1. David N. Louis et al. WHO Classification of Tumours of the Central Nervous System.

2. Osborn. Osborn’s Brain.

3.DOI: https://doi.org/10.18791/nsatlas.v1.03.01.30

(source:internet, reference only)

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