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?
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
ALL
AML
Mixed phenotypic leukaemia
Undifferentiated leukaemia