Myeloperoxidase (MPO)- Myeloperoxidase is an enzyme located in the granules of myeloid and monocytic cells. Myeloperoxidase is never found in lymphoid cells. If positive, is the most important marker distinguishing myeloid from lymphoid blasts.

Myeloblast: concentrated in the Golgi region

Monoblast: usually negative, or fine, scattered MPO-positive granules

Nonspecific esterase (NSE) - Alpha naphthyl acetate esterase is an enzyme found in large amounts in monocytic cells, but in only minor concentrations in myeloid or lymphoid cells. Useful to identify monocytes.

Mono: diffuse cytoplasmic activity, totally inhibited by sodium fluoride

Lymphoblast, megakaryoblast, erythroblast: focal punctuated activity, partially resistant to sodium fluoride

Histeocyte: ANBE & F-ANBE (+)

PAS - The periodic acid Schiff stain demonstrates glycogen and related mucopolysaccharides. Myeloid or monocytic blasts are typically weakly positive or negative. A granular (may be fine, coarse, or block) PAS pattern with a negative background is characteristic of lymphoblastic leukemia. PAS staining is positive in the erythroid population in erythroblastic leukemias (large globules).

Acid phosphatase (AP) - Although the acid phosphatase enzyme is ubiquitous, T-lymphocytes and lymphoblasts have a characteristic "dot-like" focus of intense positivity, whereas the activity in most other cells is diffuse.

CAE: neutrophil lineage, mast cell, neoplastic eosinophil

CAE (紅)+ANBE (藍)

A. Prussian blue iron stain. Erythroblastotic island containing iron laden hemohistiocyte nurturing surroundingerythroblasts in normal bone marrow aspirate.

B. Prussian blue iron stain. Ringed sideroblast with blue stained iron containing mitochondria in bonemarrow aspirate in 54 year old male with early myelofibrosis.

C. Peroxidase stain. Myeloid cells at various stages of maturity with positive golden brown peroxidasepositivity in peripheral blood of 33 year old female with chronic myelocytic leukemia. Note obvious blast containing two nucleoli and slight peroxidase stairjing on one side.

D. Peroxidase stain. Myeloblasts showing variable peroxidase positivity and Auer rods in peripheral bloodof 45 year old male with acute myelomonocytic leukemia.

E. Sudan black B. Myeloid cells at various stages of maturity exhibiting positive black SBB positivity insame case as C.

F. Naphthol AS-D chloroacetate esterase. Myeloblasts exhibiting fine pink NASD positivity in cytoplasm of bone marrow aspirate from 28 year old male with acute myelocytic leukemia.