Utility of arterial spin labeling for objective assessment of intratumoral microvessels in diffuse hemispheric glioma, H3 G34R-mutant: A case report and literature review.

Imaging findings of diffuse hemispheric glioma H3 G34-mutant (DHG, H3 G34m), a new variant of glioma under the World Health Organization classification, have recently been vigorously debated. Here, we report a case of DHG, H3 G34m in which objective assessments of intratumoral microvessels using arterial spin labeling (ASL) were useful for preoperative diagnosis, selection of anti-tumor drugs, and tracking therapeutic responses. The patient was a 34-year-old woman who presented with weakness in the left arm. Preoperative magnetic resonance imaging (MRI) showed no specific findings of hyperintensity on fluid-attenuated inversion recovery imaging and faint enhancement on T1-weighted imaging with contrast media in the tumor. However, ASL showed a convincing finding of high blood flow in the entire tumor, allowing identification of the tumor as malignant glioma. Tumor specimens obtained from biopsy showed that the tumor comprised low-differentiated tumor cells, abundant histiocytes, and highly dense microvessels. Immunohistochemical findings such as positive findings for H3 G34R and p53, and negative findings for IDH-1, ATRX, and OLIG2 led to the diagnosis of DHG, H3 G34m. Based on findings of hyperperfusion on ASL and detection of vascular endothelial growth factor (VEGF), we administered the anti-VEGF antibody bevacizumab. The tumor shrank significantly but remained. However, the residual tumor showed hypoperfusion on ASL, strongly suggesting tumor remission. Objective assessments of blood flow using ASL are useful in clinical practice for patients with DHG, H3 G34 showing non-specific findings on conventional MRI.