Brain tumor removal is a crucial step in therapeutic regimens. In surgical interventions, the ultimate goal is to completely resect the malignant lesion with a safe margin of healthy tissue; however, when the risk of impairing the patient′s life functions is too high, the scope of such surgeries is often limited. Therefore, tools that can enable the accurate, specific, and sensitive differentiation of cancerous and non-cancerous tissue are needed. Furthermore, the ability to quickly assess lesion types or grades can also improve surgical outcomes. Measurable features of brain tumors can be obtained via histol. imaging, genetic profiling, and metabolomic fingerprinting, which can be performed using a variety of anal. platforms. In recent years, optical, electrochem., and mass-spectrometry-based probes have been modified for use in in vivo applications. Among these methods, mass-spectrometry-based methods have yielded the most promising results due to the number of approaches enabling real-time monitoring and tumor classification.