There are controversies and conflicting hypotheses about myeloid cells within the tumor microenvironment. On one hand is the theory that macrophages need to be depleted; on the other, the idea that macrophages need to be re-programmed from M2 to M1 phenotype. There is a lot of discussion surrounding myeloid derived suppressor cells within the tumor microenvironment but the frequency, phenotype, and functional role of these cells are not well defined. Herein, we will review the current understanding of the myeloid cells within the human tumor microenvironment and their possible function with a focus on myeloid derived suppressor cells, granulocytes and macrophages. We will also explore different immunotherapeutic approaches to engage these immune cells within the tumor microenvironment. Furthermore, approaches on how we can characterize the role and function of myeloid cells within the solid tumors are described.