The Myeloperoxidase antibody has been shown to be a specific marker for myeloid cells and has been used in a panel for immunophenotyping acute lymphoblastic leukemia in bone marrow biopsies. Myeloperoxidase (MPO) is readily detected in myeloblasts and immature myeloid cells of acute myelogenous leukemia, progranulocytic leukemia, progranulocytic leukemia, monomyelocytic leukemia, erythroleukemia, myeloblastomas and other hematopoietic disorders. Aberrant MPO expression has been found to occur in non-myeloid cells in some disease states, including lung and ovarian cancers.