The MRI characteristics of diffuse neurosarcoidosis are similar to those of glioblastoma. Therefore, identification of novel biomarkers to distinguish these two diseases is needed. We found that lncRNA Survival Associated Mitochondrial Melanoma-Specific Oncogenic Non-Coding RNA (SAMMSON) was upregulated in plasma of glioblastoma patients but not in diffuse neurosarcoidosis patients comparing to healthy controls. Upregulated SAMMSON distinguished glioblastoma patients from diffuse neurosarcoidosis patients and healthy controls. MiR-622 in glioblastoma patients was inversely correlated with SAMMSON. SAMMSON overexpression caused the downregulated expression of miR-622 in glioblastoma cells, while miR-622 overexpression did not affect SAMMSON expression. SAMMSON overexpression mediated the increased proliferation rate of glioblastoma cells. MiR-622 overexpression played an opposite role and reduced the effects of SAMMSON overexpression. Therefore, plasma SAMMSON has diagnostic value for glioblastoma and SAMMSON overexpression may promote glioblastoma cell proliferation by downregulating miR-622.