**2.4. Oligodendroglioma, IDH-mutant, and 1p/19q codeleted**

**Definition**. Tumor with a diffuse growth pattern, slow growth, showing IDH mutations and the 1p/19q codeletion. Oligodendrogliomas develop many similarities with DA IDH-mut concerning clinical presentation, imagistic diagnosis, and therapeutical management.

Recently, it was suggested that presence of calcification is highly associated with 1p/19q code-

**Figure 7.** Axial T2W (a), axial (b) and coronal (c) FLAIR sequences of a left frontal oligodendroglioma.

**Figure 6.** Axial and coronal CT scan examination of a case with an hypodense left frontal lobe lesion with intratumoral

Diffuse Astrocytoma and Oligodendroglioma: An Integrated Diagnosis and Management

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*Standard MRI* reveals an hyperintense inhomogeneous lesion on T2W and FLAIR sequences, respectively, an inhomogeneous hypointense cortical-based well-delineated lesion on T1W sequences with no or discrete enhancement. Calcifications, cysts, and hemorrhagic lesions

**Advanced MRI techniques**. As for the diffuse astrocytomas, MRI spectroscopy reveals higher NAA (N-acetylaspartate) peak near 2 ppm. The mIns (myoinositol) peak is relatively higher when compared with normal brain; the reduction of peak signaling is a possible malignant transformation of tumor. The NAA/Cr (creatinine) ratio is higher in low-grade gliomas, meanwhile the ratio Cho(Choline)/Cr is higher in high-grade gliomas [64]. As it was already mentioned, 2HG peaks serve as an indicator for IMD 1 mutation. Perfusion MRI, an another physiologic imaging sequence, reveals that relative cerebral blood volume (rCBV) is reduced in low-grade gliomas (LGG) compared with high-grade ones. Increase in rCBV in a LGG is an indicator for rapid progression and possible malignant transformation (**Figure 8**) [65]. Diffusion tensor imaging (DTI) could also add some supplementary information in order to

letion and, as a consequence, has a prognosis role [63].

calcifications and discrete enhancement (a and b).

increase the heterogeneity of the lesion (**Figure 7**).

differentiate LGG from high-grade gliomas (HGG) [66].
