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