Fig 4. Human brain tumors are approximately twice as stiff as normal brain tissue.

Mean (red bar) of pooled indentations show glioma (n = 8 indentations from 1 sample), meningioma (n = 118 indentations from 18 samples), and mouse tumors implanted in mice (n = 31 indentations from 9 samples) are stiffer and more heterogeneous than normal mouse brain tissue (n = 50 from 11 samples) tested in our lab and as previously reported in literature (grey box). In contrast, metastatic lymphomas (n = 14 indentations from 3 samples from one patient) showed no significant difference between the SSM of normal brain tissue and were not as stiff as other tumors. Grey box reflects values for normal brain modulus reported in the literature using unconfined compression [40] and indentation methods [7,41–43].