In human invasive breast ductal carcinoma, tumor stromal macrophages and tumor nest macrophages have distinct relationships with clinicopathological parameters and tumor angiogenesis.

Tumor-associated macrophages play a crucial role in breast cancer progression and tumor angiogenesis. However, evaluation of tumor-associated macrophages incorporating their histological locations is lacking. The aim of this study was to clarify whether macrophages in tumor stroma and macrophages in tumor cell nests have distinctive properties in relation to pertinent breast cancer clinicopathological parameters and tumor angiogenesis. In 94 human invasive breast ductal carcinomas, tumor-associated macrophages were immunostained with anti-CD68 antibody and counted or graded according to these histological locations. Microvessels were immunostained with anti-CD34 antibody and counted for microvessel density. We found that the presence of tumor stromal and tumor nest macrophages was closely correlated (p = 0.001). Both tumor stromal and tumor nest macrophages were associated with mitotic count (p = 0.001 and p = 0.037, respectively). However, only higher tumor stromal macrophage grades were associated with higher tumor grades (p = 0.004) and negative estrogen receptor status (p = 0.007). Multivariate analysis showed that tumors with a high mitotic count score (score 3 vs. scores 1 and 2) had a higher tumor stromal macrophage density (Grades III and IV) when adjusted for tumor size, tubule formation, and estrogen receptor status (odds ratio 3.41, p = 0.010). The tumor nest macrophage count significantly correlated with the microvessel density (p < 0.001). These results imply that tumor stromal macrophages and tumor nest macrophages residing in different tumor microenvironments have distinctive roles.