Aim:Meningiomas are the most frequently diagnosed primary central nervous system (CNS) neoplasms. Considering slightly higher incidence of meningiomas in breast cancer patients and breast cancer in meningioma patients, it can be assumed that both tumors share similar risk factors. HER2 gene amplification and/or over-expression have been found in several human cancers, but it has been most widely studied in breast carcinomas. Bearing in mind the association of breast cancer and meningioma, the present study aimed to investigate the levels of the soluble extracellular domain of HER2 protein in meningioma cases and control group. Besides, in the present research, its associations with pathological features and prognostic indicators of meningioma were examined.Material and Methods:In the present study, 68 meningioma patients along with 20 healthy age-sex matched individuals, as controls, were selected. Levels of HER2 in the sera were measured by a quantitative enzyme-linked immunosorbent assay (ELISA). Results:The observations showed that HER2 serum levels in meningioma patients were significantly lower than normal controls. However, outlier quantities were mostly observed in the cases. Furthermore, in meningiomas with higher histological grade (grade II, III), statistically significant elevated serum levels of HER2 were observed compared to patients with low-grade meningiomas (grade I).Conclusion:The results showed that serum HER2 levels were a poor biomarker for determination of pathological and prognostic characteristics of meningiomas and coupling serum HER2 levels with immuno-histo-chemistry (IHC) examination of HER2 in meningioma tissue samples would be helpful in future studies.