SLC44A1::PRKCA fusion-positive glioneuronal tumor without histological and epigenetic features of papillary glioneuronal tumor

To the Editor: Among central nervous system (CNS) tumors, SLC44A1::PRKCA fusions have been primarily reported in papillary glioneuronal tumor (PGNT).1–4 Here, we present the case of a low-grade glioneuronal tumor harboring a SLC44A1::PRKCA fusion but lacking PGNT morphology, with comprehensive characterization by sequencing and copy number and methylation profiling. The patient was a 39-year-old man with history of migraines who presented for evaluation of increasing headache frequency. He had no history of paroxysmal neurological symptoms that would suggest epileptic seizures; however, an electroencephalogram was not performed to exclude the possibility that the symptoms were associated with epileptic auras or seizures. Imaging studies revealed a 2.2-cm right frontal well-circumscribed, calcified, partially cystic, and focally enhancing mass for which he underwent gross total resection. The entire tumor specimen was submitted for analysis. Histologic evaluation demonstrated a neoplasm with diffuse coarse calcifications (Figure 1A) that was comprised predominantly of an atypical glial component with abundant, fibrillary cytoplasm and relatively monomorphic nuclei (Figure 1B). The neoplastic cells showed immunoreactivity for OLIG2 and GFAP (Figure 1C). A neuronal component was also present, with immunoreactivity for chromogranin (Figure 1D). No papillary or pseudopapillary architecture, biphasic pattern, binucleated neurons, Rosenthal fibers, eosinophilic granular bodies, or mitotic activity were identified. The Ki67 labeling index was less than 1%.