The most aggressive primary brain tumors in adults, glioblastomas, are characterized by a profound local and systemic immune suppression. During tumor progression, the infiltration of inflammatory leukocytes, especially of myeloid origin, endowed with immunosuppressive function is observed. Aim of this study is to evaluate myeloid cell infiltrate and iron metabolism in tumor-associated macrophages by combining a multimodal MRI imaging technique with immunophenotyping of the tumor microenvironment.