The mononuclear phagocyte system of human lymphoid tissue comprises macrophages and dendritic cells (DCs). The heterogeneity of the non-DC mononuclear phagocyte population in human lymphoid tissue has been little addressed. Here, we studied the expression of 2 monocyte-derived markers, CD14 and CD169 (sialoadhesin), in reactive human lymphoid tissue as well as in a series of 51 B-cell lymphomas by immunohistochemistry on paraffin-embedded tissue. We confirmed that lymph node sinusoidal monocyte-derived cells were the only population staining for CD169. Although most sinusoidal histiocytes also expressed CD14, monocyte-derived cells with phagocytosis such as erythrophagocytosis, anthracosis, or tingible bodies macrophage lacked CD14 and CD169. Among B-cell lymphomas, splenic marginal zone lymphoma was the only one associated with an expansion of the CD14(+)CD169(+) cells in the cords. With respect to nodal B-cell lymphomas, CD14(+) cells were rare among B-chronic lymphocytic leukemia, follicular lymphoma (FL), mantle cell lymphoma (MCL). However, strikingly, we found a strong expansion of CD14(+)CD169(-) cells in numerous diffuse large B-cell lymphomas (DLBCLs), except in cases associated with numerous mitoses, apoptotic bodies, and tingible bodies macrophages. When cultivated in granulocyte/macrophage colony stimulating factor/interleukin 4, DLBCL purified CD14(+) cells differentiate into plasmacytoid cells, expressing DC-specific intercellular adhesion molecule 3-grabbing nonintegrin, suggesting dendritic cell differentiation potential. Our observation fits well with the lymph node and host response cluster signatures described in the gene profiling signatures of DLBCL. However, the role of this CD14(+) population that may constitute a microenvironment-related marker of this subgroup of DLBCL remains to be determined.