Clinical, pathologic, and genomic characteristics of two pediatric glioneuronal tumors with a CLIP2::MET fusion.

Integration of molecular data with histologic, radiologic, and clinical features is imperative for accurate diagnosis of pediatric central nervous system (CNS) tumors. Whole transcriptome RNA sequencing (RNAseq), a genome-wide and non-targeted approach, allows for the detection of novel or rare oncogenic fusion events that contribute to the tumorigenesis of a substantial portion of pediatric low- and high-grade glial and glioneuronal tumors. We present two cases of pediatric glioneuronal tumors occurring in the occipital region with a CLIP2::MET fusion detected by RNAseq. Chromosomal microarray studies revealed copy number alterations involving chromosomes 1, 7, and 22 in both tumors, with Case 2 having an interstitial deletion breakpoint in the CLIP2 gene. By methylation profiling, neither tumor had a match result, but both clustered with the low-grade glial/glioneuronal tumors in the UMAP. Histologically, in both instances, our cases displayed characteristics of a low-grade tumor, notably the absence of mitotic activity, low Ki-67 labeling index and the lack of necrosis and microvascular proliferation. Glial and neuronal markers were positive for both tumors. Clinically, both patients achieved clinical stability post-tumor resection and remain under regular surveillance imaging without adjuvant therapy at the last follow-up, 6 months and 3 years, respectively. This is the first case report demonstrating the presence of a CLIP2::MET fusion in two pediatric low-grade glioneuronal tumors (GNT). Conservative clinical management may be considered for patients with GNT and CLIP2:MET fusion in the context of histologically low-grade features.

Neuropathologic Impacts of JAK Inhibitor Treatment in Aicardi-Goutières Syndrome.

Aicardi-Goutières syndrome (AGS) is a genetic interferonopathy characterized by upregulation of type I interferon response. It is associated with increased mortality and severe disabilities. Janus Kinase (JAK) inhibitors have shown effectiveness in treatment of AGS through blocking the downstream effects of interferon activation. We illustrate post-mortem histopathologic findings in a patient with AGS who received baricitinib treatment for a duration of over 4 years, initiating at a remarkably young age of 2 months. We observed global cerebral atrophy, markedly diminished white matter, abundant calcifications involving supratentorial white matter, basal ganglia, dentate nuclei, and brainstem. This study showed profound central nervous system (CNS) sequelae despite early initiation of treatment. Our findings highlight the potential necessity for therapeutic options with enhanced CNS bioavailability.