All leucocytes display CD45 (lymphocyte common antigen), a receptor-linked protein tyrosine phosphatase that is essential to the operation of these cells. An antigen present on lymphoid cells is recognised by LCA antibodies. It reacts with granulocytes, monocytes, macrophages, T-cell subtypes, B-cells, and T-cell subtypes. When lymphoma is suspected, the CD (cluster of differentiation) is utilised to help with the differential diagnosis of undifferentiated neoplasms. Most lymphocytes contain this antibody, which is virtually exclusively expressed by cells of the hematopoietic lineage. Anti-CD45 LCA is therefore aimed against CD45 and can be used to help distinguish between healthy and aberrant leukocytic cells as well as to help with the diagnosis of anaplastic malignancies.