Fig. 1.

The anatomic distribution of brainstem tumors that underwent CSF-derived ctDNA sequencing and methods used to collect samples. The majority of patient tumors in this study are diffuse intrinsic pontine glioma (DIPG), or medullary tumors, while the remaining are other brainstem tumors also located in eloquent regions of the brain. Due to their anatomic locations, procedures such as surgical resection and stereotactic biopsy are challenging and may harbor risks for patients. Circulating tumor DNA is shed into the CSF and was isolated in our study by either VP shunt, during surgery, or by lumbar puncture