Interestingly, the absolute difference in normalized gene expression of all genes analysed between low- and high-grade astrocytoma was the largest for GFAP. Grade II versus IV showed an absolute difference in GFAP expression of 3.57E5 normalized counts and grade III versus IV of 2.20E5 normalized counts. The gene discussed is GFAP; the disease is astrocytoma (excluding glioblastoma).