A 6 year old child presents with pallor that required two blood transfusions previously. He has now developed fever and petechial haemorrhages.His hemoglobin is 9 g/dL, platelet count is 20,000/mm3 and TLC is 60,000/ mm3. Flow cytometry reveals the cells to be CD10 +ve, MPO +ve, CD 19 +ve, CD 33 –ve, CD 117 +ve, and CD3 –ve.
Which of the following is the most likely diagnosis?: (A) ALL, (B) AML, (C) Mixed phenotypic leukaemia, (D) Undifferentiated leukaemia
Answer is C. Mixed lineage acute leukemia is alternatively also known as bilineal acute leukemia. As suggested by the name, there are 2 populations of cells which are morphologically and immunophenotypically distinct from each other.
Analyzing the markers on the cells,

B lymphoid markers: CD10, CD19 and CD79.
T lineage markers: CD2, CD3 and CD7.
Myeloid markers; CD13, CD33, CD117 and myeloperoxidase (MPO).
Non lineage specific markers which are expressed in hematopoietic progenitor cells: CD34, HLA-DR and TdT. Comparing this with the information provided in the stem of our question, it is easy to decipher that the cells mentioned are CD10+ve, MPO +ve, CD19+ve, CD33-ve, CD117 +ve and CD3-ve which is showing both lymphoid (CD10, CD19;B lymphoid lineage) and myeloid (CD117 and MPO+-; myeloid lineage) markers.

So, the answer is
Mixed phenotypic leukemia
A word about the last option ‘d’, please note that in un-differentiated acute leukemia, blasts usually lack any evidence of lineage differentiation.
Wintrobes 12th/1814-8