Myeloid Cell Marker : CD 15

CD15 (Lewis X) is commonly used as a myeloid/granulocyte marker in immunohistochemistry and flow cytometry—strongly expressed on neutrophils, other granulocytes and myeloid precursors. However, it isn’t entirely specific: CD15 can appear on subsets of monocytes, certain B cells and Hodgkin Reed–Sternberg cells. CD15 should be interpreted alongside other markers and morphology for accurate lineage assignment.

CD15 positive means cells express the CD15 cell-surface antigen (a carbohydrate/Lewis X–related marker). It’s commonly found on granulocytes and some monocytes and is used in immunohistochemistry to indicate myeloid/granulocytic differentiation. CD15 positivity can support diagnoses such as certain leukemias or classical Hodgkin lymphoma (Reed–Sternberg cells), but it isn’t definitive alone and requires clinical correlation.

CD15 is characteristically positive in classical Hodgkin lymphoma (Reed–Sternberg cells). It is also expressed in myeloid neoplasms (e.g., acute myeloid leukemia with myelomonocytic differentiation) and can be seen in various epithelial malignancies—notably colorectal, gastric, pulmonary (adenocarcinoma), and ovarian carcinomas—and occasionally in other epithelial or urothelial tumors.

Myeloid cells typically express CD11b, CD13, CD14 (monocytes/macrophages), CD33 (myeloid progenitors), CD15 and CD66b (granulocytes/neutrophils), CD16 and CD64 (Fc receptors on neutrophils/monocytes), CD68 (macrophages), and HLA-DR (monocytes/dendritic cells). Early myeloid progenitors may also show CD34 and CD117 (c‑Kit). Marker expression varies with maturation and activation.

Leukemia immunophenotypes: B‑cell ALL — CD19, CD10, CD22 (±CD20), CD34, TdT; T‑cell ALL — cytoplasmic/surface CD3, CD2, CD7, CD5, CD1a; AML — myeloid markers CD13, CD33, CD117, CD34, HLA‑DR, with monocytic CD14/CD64; CLL — co‑expression of CD19 with CD5 and CD23 (dim CD20); hairy cell — CD11c, CD25, CD103. CD45 is a pan‑leukocyte marker used in flow cytometry.

CD15 (Lewis X) is a carbohydrate cell-surface marker expressed on granulocytes, monocytes and some tumor cells. It mediates cell–cell adhesion and recognition, supporting neutrophil rolling, migration, phagocytosis and immune targeting. Clinically, CD15 is used in immunophenotyping to identify granulocytic lineage and aid diagnosis of certain malignancies such as classical Hodgkin lymphoma and some myeloid leukemias.