In the clinical samples, TSPO levels proved highest in grade III and IV infiltrating gliomas, whereas low-grade tumors (grade I pilocytic astrocytoma) expressed TSPO levels just above non-tumor background, suggesting that TSPO PET could potentially serve as a non-invasive indicator of glioma grade and better evaluate disease extent, especially white-matter infiltration, compared to current standard-of-care imaging. The gene discussed is TSPO; the disease is neoplasm.