**3.2. Anaplastic astrocytoma, IDH wild-type**

**Definition**. Tumoral proliferation which, from a histopathological point of view, displays an astrocytic phenotype with a diffuse growth pattern, proliferative activity, and increased anaplasia, and which, genetically speaking, does not feature mutations in the IDH gene.

**Grading**. Grade III tumor.

**Grading**. Diffuse astrocytoma is deemed grade III WHO.

archive) suggesting a hereditary determinism in this particular case.

110 Glioma - Contemporary Diagnostic and Therapeutic Approaches

rological deficits in more advanced stages.

opaque. Cysts are rarely encountered.

*Clinically*, the patients experience seizures, headache, neurocognitive disturbances, and neu-

**Figure 13.** Upper row: left frontal lesion hyperintense in T2W (a) and FLAIR (b) sequences with no contrast and T1W sequence (c) MRI in a 24 years old men diagnosed with grade III astrocytoma; lower row: left frontal lesion having similar characteristics in T2W (d) and FLAIR (e) sequences but with a discrete enhancement in T1W (f) sequences revealed in the young men's father MRI examinations, operated 5 years before with an anaplastic astrocytoma (personal

**Imaging**. MRI features are quite variable, with isointense mixed with hypointense signaling on T2 W sequences and heterogeneous hyperintensity in T2W and FLAIR sequences. The contrast enhancement is subtle or is lacking in majority of cases [75] (**Figures 13** and **14**).

**Macroscopy**. Anaplastic astrocytoma appears as an expansion of the tissue tending to infiltrate the surrounding nervous structures, but without destroying them. It is difficult to distinguish from the grade II astrocytoma, but the increased cellularity makes it easier to identify the edges of the tumor. Also, in cross section, we see areas of low consistency, granular, or

**Histological diagnosis**. The aspect is that of a tumoral proliferation with astrocytic phenotype and a diffuse growth pattern. As compared to grade II astrocytomas, it shows increased cellularity, anaplasia, and mitotic activity. These three parameters can vary between grade II astrocytoma and glioblastoma and must therefore be assessed in context. A heightened mitotic activity is sufficient for a diagnosis, even if the cellularity is low or normal. Also, just one mitosis in a stereotactic biopsy can be sufficient for a diagnosis. There are also atypical mitoses. In a large biopsy,

**Genetic diagnosis**. One in five anaplastic astrocytomas does not feature the IDH mutation, the genetic profile and the clinical evolution of these tumors being that of wild-type glioblastoma.
