Role of tumor-associated macrophage in malignant tumors: should the location of the infiltrated macrophages be taken into account during evaluation?

Tumor-associated macrophages (TAMs) have a complex relationship with the tumor cells. Because TAMs have various functions according to the microenvironment, the results of many analyses have not led to a general consensus regarding the role of TAMs in solid tumor tissue and the prognostic significance for patients. In this review, we discuss whether the recently published data can help to explain the apparent paradoxical effects of TAMs in cancers. We address this question on the basis of the histological location of TAMs in solid malignant tumors.