The MYB genes encode transcription factors that are involved in the cell cycle. Alterations in MYB genes have been observed in multiple cancers. In 2021, the World Health Organization added MYB/MYB1 altered diffuse astrocytomas to its Classification of Tumors of the Central Nervous System as a tumor type within pediatric-type diffuse low-grade gliomas.

MYB/MYB-1 altered diffuse astrocytomas are low-grade pediatric-type gliomas with structural variations in MYB or MYBL1. They occur in the pediatric population (median age of diagnosis of 5 years), have pathologic findings congruous with low-grade gliomas, and are typically found in the cortex, supratentorial white matter, or the brainstem. On MRI, they are seen as T2-hyperintense, non-enhancing, non-diffusion-restricting masses. They are considered WHO Grade 1.

This case reveals a newly defined tumor type that, to our knowledge, has yet to be reported within the spinal cord or in the adult population. Typically, CNS tumors with alterations in MYB/MYB-1 occur in the pediatric population and are located within the brain. This case demonstrates that MYB-altered astrocytomas can be found in the adult population and can occur in the spinal cord. The characteristics of this tumor are important to note as updates are continually being made to tumor classification systems and as novel cancer therapeutics are developed.