Papillary glioneuronal tumor (PGNT) is a rare, World Health Organization (WHO) Grade I mixed glioneuronal neoplasm characterized by the presence of both neuronal and glial elements. It commonly presents with seizures or headaches and has a generally favorable prognosis after gross total resection. Here, we present an unusual case of PGNT with deep hemispheric extension involving the centrum semiovale, temporal lobe, and mesencephalon in a pediatric patient. A 6-year-old male patient presented with a history of two partial epileptic seizures over the past 3 months. On admission, neurological examination was unremarkable. Personal and family histories were non-contributory. Initial cranial magnetic resonance imaging (MRI) revealed a heterogeneous T2-hyperintense, T1-hypointense, noncontrast-enhancing lobulated lesion extending from the left centrum semiovale to the temporal lobe and mesencephalon with minimal rightward midline shift. The patient underwent left frontoparietal craniotomy and microsurgical excision under neuronavigation. Given the tumor's eloquent location, a safe subtotal resection was performed. Histopathological evaluation revealed a WHO Grade I PGNT with glial fibrillary acidic protein, Olig2, and synaptophysin positivity and a low Ki-67 proliferation index (2-3%). Postoperatively, the patient had no neurological deficits and was discharged on the 7th day. A follow-up MRI is planned at 6 months. This case underscores the need to include PGNT in the differential diagnosis of pediatric patients presenting with new-onset focal seizures and MRI findings suggestive of a low-grade glioma. Surgical management is typically curative, resulting in excellent seizure control and long-term outcomes.

Low-grade epilepsy-associated tumors (LEATs) are a distinct group of tumors commonly encountered in pediatric drug-resistant epilepsy that necessitate surgical intervention. Like tumors elsewhere in the central nervous system, molecular characterization is becoming an increasingly important consideration in pediatric neuro-oncology prognostication and management for LEATs. Thus, familiarity with relevant tumor mutations and radiogenomic features of LEATs is important for radiologists caring for affected patients. This article will review the genetic alterations and imaging characteristics of LEATs, formatted according to the three categories defined by the World Health Organization (WHO): glioneuronal and neuronal tumors (ganglioglioma, dysembryoplastic neuroepithelial tumor, papillary glioneuronal tumor, multinodular and vacuolating neuronal tumor); circumscribed astrocytic gliomas (pilocytic astrocytoma, pleomorphic xanthoastrocytoma); and pediatric-type diffuse low-grade gliomas (diffuse astrocytoma MYB or MYBL1-altered, angiocentric glioma, diffuse low-grade glioma MAPK pathway-altered, polymorphous low-grade neuroepithelial tumor of the young).

Glioneuronal and neuronal tumors are defined histologically by the presence of mixed glial and neuronal elements in the case of glioneuronal tumors, and by neuronal elements in the case of neuronal tumors. In 2021, the World Health Organization (WHO) published the latest edition of central nervous system tumor classifications and added three new glioneuronal tumors, as well as further delineated histological, immunohistochemical, and molecular markers associated with the diagnosis of these tumors. This review aims to highlight the key updated features of glioneuronal and neuronal tumors in adults based on the 5th edition of the WHO classification of central nervous system tumors by clinical and epidemiological presentation, imaging appearance, and pathology.ABBREVIATIONS: DGONC = diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters; DLGNT = diffuse leptomeningeal glioneuronal tumor; DNET = dysembryoplastic neuroepithelial tumor; LEAT = long term epilepsy associated tumor; MGNT = myxoid glioneuronal tumor; MVNT = multinodular and vacuolating neuronal tumor; PGNT = papillary glioneuronal tumor; RGNT = rosette-forming glioneuronal tumor; WHO = World Health Organization.

Papillary glioneuronal tumors (PGNTs) are classified by the World Health Organization (WHO) as Grade I neoplasms, with only sporadic reports of anaplastic variants demonstrating aggressive clinical behavior and distinct histopathological characteristics. This study presents two cases of anaplastic PGNT, including one that ultimately progressed to glioblastoma (WHO Grade IV). The first case involved a 47-year-old female patient without a history of seizures. Magnetic resonance imaging (MRI) revealed an irregular mass containing multiple cysts and a mural nodule in the left parietal lobe. Histopathological examination confirmed the diagnosis of anaplastic PGNT. Nineteen months later, follow-up brain MRI demonstrated a recurrent mass at the prior surgical site. During the second resection, histological analysis identified glioblastoma arising from the glial component of the original tumor. The second case concerned a 7-year-old boy presenting with progressive headache. MRI showed a solid-cystic mass in the right frontal lobe accompanied by marked peritumoral edema. Postoperative pathological examination revealed anaplastic PGNT with extensive necrosis. MRI characteristics including prominent peritumoral edema, ring-enhancing cyst walls, restricted diffusion, and elevated lipid/lactate peaks may predict the aggressive nature of anaplastic PGNT. Furthermore, this case series suggests that anaplastic PGNTs harbor malignant potential to transform into more aggressive neoplasms.