Cluster of differentiation 14 (CD14) is a macrophage-derived monocyte marker which stains granulocytes, endothelial and epithelial cells, placental trophoblasts, and the red pulp and marginal zone cells of the spleen. In lymph nodes, sinusoidal histiocytes and follicular dendritic cells stain positively for CD14, while monocyte-derived cells, including macrophages associated with anthracosis and sinusoidal histiocytosis with erythrophagocytosis, stain negatively. Plasmacytoid dendritic cells are devoid of CD14. High CD14 expression is found in histiocytes with Diffuse Large B-Cell Lymphoma (DLBCL) when compared to Chronic Lymphocytic Leukemia (CLL)/Small Lymphocytic Lymphoma (SLL), Mantle Cell Lymphoma (MCL), or Follicular Lymphoma (FL). A panel of S100, CD68, and CD14 is useful for recognizing Rosai-Dorfman disease. CD14 staining identifies increases in myelomonocytic and monocytic neoplastic cells in chronic myelomonocytic leukemia, and detects monocytic leukemia from decalcified bone marrow biopsy samples. CD14 is valuable for differentiating between acute monocytic leukemia, myeloproliferative neoplasms, and myelodysplastic syndrome.