Additional Considerations for Accurate and Timely Diagnosis of DMG

Funding support provided by Chimerix/Jazz Pharmaceuticals. Content independently developed and published by OncLive.

Intraoperative pathology for diffuse midline glioma requires meticulous handling of very limited biopsy samples. Because tissue obtained from delicate brain regions is often only a few millimeters in size, pathologists must balance the need to confirm diagnostic viability with the need to preserve material for downstream testing. A common mistake is overusing tissue for frozen sections, which can exhaust the sample and leave nothing for molecular studies. To avoid this, only a small portion is typically smeared to assess cellularity while preserving the core of the biopsy for further analysis. This approach ensures enough material is available for sequencing, which is essential to guide treatment decisions.

Effective communication and trust between the pathologist and neurosurgeon are critical to this process. If the initial smears suggest only reactive changes or inconclusive findings, the pathologist may request additional small samples while the patient is still in the operating room. This collaboration minimizes the risk of obtaining non-diagnostic tissue and prevents the need for repeat biopsies, which carry additional risks. Cutting protocols in histopathology also play a role; requesting a larger batch of unstained slides up front helps preserve tissue by reducing the number of times the block is recut. This strategy maximizes the availability of slides for both immunostaining and molecular testing, ensuring diagnostic flexibility without exhausting the sample.

Neuroradiology also plays an important role in guiding biopsies toward the most diagnostically valuable regions. Since many diffuse midline gliomas show little or no contrast enhancement, additional imaging strategies are needed to identify high-yield targets. Subtraction imaging can highlight subtle areas of enhancement, while diffusion-weighted MRI offers an especially useful tool. Hyperintense regions on diffusion scans often correspond to areas of anaplasia, making them ideal surgical targets when other advanced modalities are unavailable. This integration of pathology and imaging expertise enhances diagnostic yield while protecting patients from unnecessary risk.