Stains & CD markers
Myeloperoxidase (MPO)


Last author update: 26 February 2024
Last staff update: 26 February 2024

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PubMed Search: Myeloperoxidase

Nat Pernick, M.D.
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Cite this page: Pernick N. Myeloperoxidase (MPO). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsmyeloperoxidase.html. Accessed April 14th, 2024.
Definition / general
  • Myeloid marker that stains neutrophils strongly, other granulocytes variably
  • Staining is either via immunohistochemistry (IHC), enzyme cytochemistry or flow cytometry (see Interpretation for details) (Br J Haematol 2021;193:922)
Essential features
  • Myeloid marker that stains neutrophils strongly, other granulocytes variably
  • Myeloid marker useful for initial screening of primary marrow disorders and acute myeloid leukemia (AML) subtyping
Terminology
Pathophysiology
Clinical features
  • Detected in > 80% of AML blasts
  • Isolated MPO positivity is associated with unfavorable prognostic factors in B cell acute lymphoblastic leukemia (B ALL) in adults, including lower overall survival (Asian Pac J Cancer Prev 2021;22:2143)
  • Isolated MPO expression can be detected, most commonly by IHC but also by flow cytometry, contributing to misdiagnosis in B ALL in adults (Asian Pac J Cancer Prev 2021;22:2143)
  • In extensive, longstanding ulcerative colitis, MPO expression is associated with ulcerative colitis - colorectal cancer (Inflamm Bowel Dis 2012;18:275)
Interpretation
  • IHC: most sensitive technique in discrepant cases (Indian J Hematol Blood Transfus 2018;34:233)
  • Enzyme cytochemistry: sensitive and specific for myeloid leukemias and myeloid (granulocytic) sarcoma
    • Useful to distinguish acute promyelocytic leukemia (APL) and myelomonocytic / monocytic leukemia
    • Useful to diagnose mixed phenotype acute leukemias (Am J Hematol 2016;91:856)
  • Flow cytometry: useful for diagnosis and classification of acute leukemias and for diagnosis of myelodysplastic syndrome in peripheral blood (Blood 2018;132:5194, Br J Haematol 2021;193:922, Haematologica 2019;104:2382)
  • Diffuse granular staining pattern of MPO in neutrophil cytoplasm is due to staining of primary granules
Uses by pathologists
  • For primary marrow disorder initial screening, along with CD34, CD61, CD71 and CD117
  • For AML subtyping
  • To distinguish chronic myelomonocytic leukemia from acute myeloid leukemia with monocytic differentiation as part of a comprehensive panel (Histopathology 2012;60:933)
    • Note: Sudan Black B can be used as a substitute in patients with myeloperoxidase deficiency
  • For enzyme cytochemistry, fresh smears are preferred; if not possible, store unstained slides away from light
Microscopic (histologic) description
  • Diffuse granular staining pattern of MPO is present in neutrophils and other myeloid cells due to staining of primary granules
Microscopic (histologic) images

Contributed by Carolina Martinez Ciarpaglini, M.D., Ph.D. (Case #429), Yen-Chun Liu, M.D., Ph.D., Angel Fernandez-Flores, M.D., Ph.D. (Case #151), K.V. Vinu Balraam, M.D. and S. Venkatesan, M.D. (Case #463) and AFIP
Myelocytes and promyelocytes in extramedullary hematopoiesis Myelocytes and promyelocytes in extramedullary hematopoiesis

Myelocytes and promyelocytes in extramedullary hematopoiesis (EMH)

Normal bone trabeculae

Normal bone trabeculae

AML M0 is MPO negative

AML M0 is MPO negative

AML M1

AML M1


AML M2

AML M2

Myeloid sarcoma: myeloblasts are MPO+

Myeloid sarcoma: myeloblasts are MPO+

Leukemia cutis

Leukemia cutis

CML: MPO negative

CML: MPO negative

Positive staining - normal
Negative staining - normal
Electron microscopy description
Sample pathology report
  • Bone marrow, biopsy:
    • Acute myeloid leukemia with mutated NPM1 (see comment)
    • Comment: The bone marrow is massively infiltrated by blasts with a myelomonocytic appearance. By immunohistochemistry, they express cytoplasmic NPM1 and coexpress myeloperoxidase and macrophage restricted CD68 but CD34 is negative.
Board review style question #1

Which of the following entities are typically myeloperoxidase positive by immunocytochemistry or enzyme cytochemistry?

  1. Acute erythroid leukemia (AML M6)
  2. Acute lymphoblastic leukemia
  3. AML with minimal differentiation (FAB AML M0)
  4. AML without maturation (FAB AML M1)
Board review style answer #1
D. AML without maturation (FAB AML M1). In AML without maturation (FAB AML M1), the myeloblasts are positive for myeloperoxidase. Answers A, B and C are incorrect because these entities are typically negative for myeloperoxidase, although acute lymphoblastic leukemia can show isolated myeloperoxidase positivity.

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Reference: Myeloperoxidase
Board review style question #2
Which normal cells are typically strongly myeloperoxidase positive by immunocytochemistry or enzyme cytochemistry?

  1. Basophils
  2. Lymphocytes
  3. Megakaryocytes
  4. Neutrophils
Board review style answer #2
D. Neutrophils. Myeloperoxidase strongly stains the primary granules in neutrophils. Answers A, B and C are incorrect because myeloperoxidase does not strongly stain basophils (immature forms are MPO+), lymphocytes (some subsets are weakly positive) or megakaryocytes.

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Reference: Myeloperoxidase
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