Tumor-associated macyophages (TAM) have a complex relationship with the neoplastic cells of the tumor. 0~ the one hand, the ttoo cell types produce reciprocal growth factors and may be considered to have a symbiotic relatiorrship. On the othey hand, TAM ctzn he activated to inhibit tumor growth ami destroy neoplastic cells. Here, Alberta Mantovani aml colleagues describe this delicate balance and the prospects fos its theyapezttic mnipulatiorr.

In 1X63, Virchow first identified host leukocytes in and/or at the edge of tumor tissue. He proposed that the frequent occurrence of a lymphoreticular infiltrate in human neoplasms retlected the origin of cancer at sites of previous chronic inflammation. However, when, in 1907, Hardley reported that normal cell infiltration in malignant melanoma indicated a ‘regressive process’, opinion as to the significance of the ‘lymphoreticular infiltrate’changed, reflected by numerous reports on pathology and prognosis. These conflicting views of the relationship between leukocyte infiltration and malignancy reflect the pleiotropic, ambivalent functions of infiltrating cells, functions that are now being explored at the molecular level. This macrophage balance is illustrated in Fig. I.