In breast carcinoma tissue, immature dendritic cells reside within the tumor, whereas mature dendritic cells are located in peritumoral areas

We have analyzed the presence of immature and mature dendritic cells (DCs) within adenocarcinoma of the breast using immunohistochemistry. Immature DC S were defined by expression of CD1a-, Langerin-, and intracellular major h istocompatibility complex class II-rich vesicles. Mature DCs were defined b y expression of CD83 and DC-Lamp. Breast carcinoma cells were defined by mo rphology and/or cytokeratin expression. We demonstrate two levels of hetero geneity of DCs infiltrating breast carcinoma tissue: (a) immature CD1a(+) D Cs, mostly of the Langerhans cell type (Langerin(+)), were retained within the tumor bed in 32/32 samples and (b) mature DCs, CD83(+) DC-Lamp(+), pres ent in 20/32 samples, are confined to peritumoral areas. The high numbers o f immature DCs found in the tumor may be best explained by high levels of m acrophage inflammatory protein 3 alpha expression by virtually all tumor ce lls. Confirming the immature/mature DC compartmentalization pattern, in vit ro-generated immature DCs adhere to the tumor cells, whereas mature DCs adh ere selectively to peritumoral areas. In some cases, T cells are clustering around the mature DCs in peritumoral areas, thus resembling the DC-T cell clusters of secondary lymphoid organs, which are characteristic of ongoing immune reactions.