To address this issue, we explore in the present study the plasma membrane morphology in five GBM lines differing in the mutational status of PTEN and p53. In addition to scanning electron microscopy (SEM), we applied the electrorotation (ROT) technique to quantify the area-specific membrane capacity Cm [μF/cm2], related to membrane folding, and the whole-cell capacitance CC [pF], which reflects the total membrane area [36]–[38]. Here, PTEN is linked to glioblastoma.