Organ Systems, WHO Classification, Hematopathology, Acute Leukemia

WHO 2008/2016 Criteria for Mixed-Phenotype Blasts

Myeloid

  • MPO expression (flow cytometry, immunohistochemistry, or enzyme cytochemistry) – WHO does not define thresholds for positiivity, which can result in variability between laboratories
    • Flow cytometry:  >10% (some propose 13%) expression compared to isotype control (preferred methodology)
    • Enzyme cytochemsitry:  >3% staining of blasts
    • IHC:  No well-defined cutoff (not commonly done – MPO IHC is available)

T-Lineage

  • Strong (equal to or greater than normal lymphocytes) cytoplasmic CD3
  • (or) Surface CD3

B-Lineage

  • Strong CD19 plus strong expression of 1 of the following
    • CD79a
    • Cytoplasmic CD22
    • CD10
  • (or) Weak CD19 with strong expression in at least 2 of the following
    • CD79a
    • Cytoplasmic CD22
    • CD10
EGIL Algorithm for Biphenotypic Blasts
Mixed Phenotypic Acute Leukemias (MPAL)
References

Swerdlow SH, Campo E, Harris, NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):  WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017