With the increasing discovery of molecular markers in glioma, qq is an important molecular diagnostic marker in addition to IDH1/2 and TERT. Its joint deletion and IDH1/2 co-mutation are used as diagnostic markers for oligodendroglial cell tumors in the 2016 edition of the WHO Classification of Tumors of the Central Nervous System guidelines. The 1p/19q co-deletion is a chromosomal variant that refers to the simultaneous deletion of the short arm of chromosome 1 and the long arm of chromosome 19, often occurring in young patients. the end of the short arm of chromosome 1 concentrates a high density of genes associated with cell growth, proliferation, and differentiation, making this region a hot spot for molecular cytogenetic studies of tumors. The 1p/19q co-deletion was first identified in oligodendroglioma samples, with an incidence of 80%-90% in oligodendrogliomas and 50%-70% in mesenchymal oligodendrogliomas, while the incidence in diffuse astrocytomas and glioblastomas is only 15% and 5%. Therefore, in 2016, the latest WHO distribution of CNS tumor classification classified oligodendrogliomas into oligodendrogliomas (WHO-II grade) and mesenchymal oligodendrogliomas (WHO-III grade),and also classified oligodendrogliomas and mesenchymal oligodendrogliomas into IDH mutant type, 1p/19q deletion according to the presence or absence of IDH1/2 gene mutation and 1p/19q deletion. 1p/19q deletion type and type not otherwise specified. Nowadays, 1p/19q deletion has been explicitly included in major guidelines such as NCCN guidelines and China Glioma Consensus. The main laboratory detection methods are fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR) based on heterozygous deletion analysis, array comparative genomic hybridization (CGH) and second generation sequencing (NGS). Detection of 1p/19q co-deletion is important in diagnosing oligodendroglioma and determining patient prognosis, and patients with IDH1/2 mutations combined with 1p/19q co-deletion have the best prognosis compared to those with 1p/19q non-deletion. Therefore, 1p/19q co-deletion is also known as the “diamond mutation” in glioma, which is an unfortunate blessing for families. The treatment of glioma is mainly surgical resection, combined with radiotherapy and chemotherapy. Oligodendrogliomas with a combined 1p/19q deletion have a slower growth rate and are more sensitive to chemotherapy (especially the PVC regimen). The average survival of patients is 10 years, compared to 2 years in patients without this genetic alteration. The previous classic RTOG9402 clinical trial also explored the effect of adding chemotherapy to radiotherapy and resulted in significantly higher median survival with the combination of radiotherapy and chemotherapy in patients with 1p/19q co-deletion than in those receiving only radiotherapy (14.7 years vs. 7.3 years). The incidence of MGMT gene promoter methylation was also relatively high in oligodendrogliomas (up to 80%). Therefore, in a study on the correlation between oligodendroglioma 1p/19q co-deletion and MGMT gene promoter methylation, it was found that oligodendroglioma 1p/19q co-deletion was positively correlated with MGMT gene promoter methylation, and both were associated with 3-year patient survival. The rates of 1p/19q co-deletion and MGMT gene promoter methylation were significantly higher in patients with survival greater than 3 years than in patients with survival less than 3 years. Pseudoprogression is now considered to be a common radiological phenomenon that occurs early in the course of glioma after receiving radiotherapy and/or chemotherapy. The presence of 1p/19q co-deletion has been shown to be associated with a low risk of pseudoprogression formation, with pseudoprogression occurring rarely in the 1p/19q co-deletion group, while the rate of pseudoprogression in the no-deletion group was 10 times higher than that in the deletion group.