Association of different macrophage phenotypes with infiltrating and non-infiltrating areas of tumor-host interface in colorectal carcinoma.

At the tumor-host interface (interface) of well differentiated tubulary or tubulopapillary colorectal carcinomas infiltrative, poorly demarcated and non-infiltrative, well bordered areas alternate. The composition of the inflammatory infiltrate within the desmoplastic stroma of the central tumor part and the interface was analyzed, particularly emphasizing differences between infiltrative and non-infiltrative areas of the interface. Of particular interest was the distribution of the following recently identified, functionally different human macrophage phenotypes: the 27E10-positive phenotype, an inflammatory macrophage, the 25F9-positive phenotype, a mature, resident macrophage and the RM3/1-positive phenotype, associated with anti-inflammatory function. It was found that macrophages were the dominating cells in the inflammatory infiltrate of both central tumor part and interface and that the number of B-cells and NK-cells were negligible. The 27E10-positive phenotype revealed a strong association with infiltrative areas at the interface, whereas the resident macrophage together with the RM3/1 was associated with sharply bordered tumor areas dominating within the tumor stroma, particularly in carcinomas with marked desmoplastic stroma response. These findings suggest that different macrophage phenotypes, localized in different regions of the carcinoma, have different effects on tumor cells.