Mixed phenotype acute leukemia (MPAL)

As defined by the World Health Organization (WHO), MPAL includes both bilineage acute leukemia (separate populations of blasts of more than one lineage) and biphenotypic acute leukemia (blasts co-expressing antigens of more than one lineage).
There are two methods for identifying MPAL:
First the European Group for Immunological Characterization of Acute Leukemias (EGIL): it assigns a weighted score to each marker depending associated with a specific lineage. Biphenotypic (or triphenotypic) leukemia is diagnosed when a score greater than 2 is calculated for more than 1 lineage, positivity defined as a positive signal on at least 20% of blasts for surface markers and at least 10% for cytoplasmic markers:
The WHO classification criteria emphasize a few key lineage-defining markers; CD19 for B lineage, CD3 for T lineage, and myeloperoxidase (MPO) for myeloid lineage. Sensitivity and specificity of these few markers are essential. Also, the WHO classification does not specify thresholds for positivity of these key markers.