DNA methylation-based reclassification of olfactory neuroblastoma

Area of Science:

• Oncology
• Molecular Pathology
• Genomics

Background:

• Olfactory neuroblastoma (ONB), a rare neuroectodermal tumor, originates from the olfactory epithelium.
• The molecular underpinnings of ONB remain largely uncharacterized.

Purpose of the Study:

• To investigate the molecular pathogenesis of institutionally diagnosed ONB.
• To identify distinct molecular subgroups within ONB using comprehensive profiling.
• To differentiate ONB from its potential mimics.

Main Methods:

• Retrospective analysis of 66 ONB tumor samples.
• Immunohistochemistry, genome-wide DNA methylation profiling, and copy number analysis.
• Next-generation sequencing (NGS) of 560 tumor-associated genes in a subset.

Main Results:

• Unsupervised clustering revealed four distinct molecular subgroups within ONB.
• A core ONB group (64%) showed classical histology and distinct methylation profiles.
• A subgroup with IDH2 mutations and cytokeratin expression clustered with sinonasal carcinoma.
• Copy number analysis identified recurrent chromosomal losses in core ONB.
• TP53 and DNMT3A were the only recurrently mutated genes in ONB.

Conclusions:

• Institutionally diagnosed ONB represents a heterogeneous group of tumors.
• DNA methylation patterns, cytokeratin/chromogranin A expression, and IDH2 mutational status are crucial for precise ONB classification.
• Molecular subtyping aids in distinguishing ONB from other sinonasal malignancies.