Leucocyte Common Antigen (LCA) : CD 45

CD45 positivity is not inherently good or bad. It’s a cell-surface marker that identifies leukocytes (white blood cells) and helps distinguish immune-cell origin from non-hematopoietic cells. Normal CD45 expression is expected on most immune cells; altered levels or atypical patterns can indicate disease and require clinical interpretation alongside other laboratory and clinical findings.

Positive CD45 (LCA) means the cells express leukocyte common antigen, indicating a hematopoietic (white blood cell) origin. In pathology this supports a diagnosis of lymphoma or leukemia rather than a non‑hematologic tumor (carcinoma, melanoma, sarcoma). It is not subtype‑specific; additional immunostains, morphology, and clinical information are needed to determine the exact diagnosis and guide management.

CD45 is a pan‑leukocyte antigen expressed on most hematopoietic cells; it is not a tumor‑specific marker. Clinically it is used in pathology and flow cytometry to identify hematopoietic origin and to classify leukemias and lymphomas. Some hematologic cancers show reduced or absent CD45, so results are interpreted with other markers and clinical context to establish diagnosis.

CD45, or protein tyrosine phosphatase receptor type C (PTPRC), is the common leukocyte antigen expressed on all nucleated hematopoietic cells. It is a transmembrane tyrosine phosphatase that regulates Src‑family kinases, antigen‑receptor signaling, and lymphocyte development and activation. Multiple isoforms arise from alternative splicing. CD45 is widely used as a pan‑leukocyte marker in immunophenotyping and flow cytometry.

CD45 refers to a family of transmembrane protein tyrosine phosphatases expressed on almost all nucleated hematopoietic cells and commonly called the leukocyte common antigen. CD45 regulates immune cell signaling, especially antigen‑receptor pathways in T and B lymphocytes, and exists in multiple isoforms that change with cell type and activation state. It is widely used as a pan‑leukocyte marker in immunology and diagnostics.

CD45 is a pan‑leukocyte marker present on essentially all white blood cells. In peripheral blood, >95% of WBCs are CD45‑positive; laboratories don’t report a separate “CD45 level” as a numeric concentration. Clinicians use CD45 gating in flow cytometry alongside the absolute WBC count (normal ~4,000–11,000/µL) to evaluate leukocyte populations. Abnormal CD45 patterns can indicate hematologic disorders.