Emerging glioneuronal and neuronal tumors: case-based review

Area of Science:

• Neuro-oncology
• Central Nervous System Pathology
• Molecular Genetics

Background:

• Glioneuronal and neuronal tumors (GNTs) are rare, heterogeneous central nervous system neoplasms.
• These tumors present diagnostic challenges despite slow growth and favorable prognoses.

Purpose of the Study:

• To analyze clinicopathological and molecular genetic features of three recently recognized GNTs.
• To differentiate and characterize spinal diffuse leptomeningeal glioneuronal tumor (DLGNT), occipital multinodular and vacuolating neuronal tumor (MVNT), and diffuse glioneuronal tumor with oligodendroglioma-like features (DGONC).

Main Methods:

• Clinicopathological analysis of three rare GNT cases.
• Molecular genetic characterization including chromosome analysis and next-generation sequencing (NGS).
• Literature review for comparative analysis.

Main Results:

• Spinal DLGNT showed oligodendroglioma-like features with 1p/19q codeletion, lacking IDH mutations and possessing KIAA1549:BRAF fusion.
• Occipital MVNT exhibited gangliocytic tumor cells with vacuolation and MAP2K1 p.Q56_V60del.
• Amygdala DGONC presented with oligodendroglia-like cells, nuclear clusters, and monosomy 14.

Conclusions:

• DLGNT commonly occurs in the spinal cord and is associated with KIAA1549:BRAF fusion.
• MVNT is a neoplasm, not a malformation, with MAP2K1 deletion as a hallmark.
• DGONC diagnosis can be achieved through unique histology, monosomy 14, and exclusion, potentially without methylation profiling.