The objective of this clinical trial is to investigate the effects of Salovum®, an egg yolk powder enriched with the endogenous protein antisecretory factor, in participants undergoing diagnostic biopsies for suspected glioblastoma. The primary questions the trial seeks to answer are: * Will Salovum® reduce intratumoral pressure? * Will Salovum® influence the release of inflammatory cytokines from tumor tissue? Additionally, the study will investigate the impact of Salovum® on intratumoral partial oxygen pressure and tumor volume. Researchers will: * Place probes for measuring intratumoral pressure, microdialysis, and partial oxygen pressure during a standard biopsy procedure. * Compare measurements from participants before and during ingestion of Salovum®. Participants will: * Have probes implanted during a surgical biopsy. * Ingest Salovum® 24 to 72 hours after the procedure.