1. Society for Hematopathology/European Association for Haematopathology 2013
Case Number 208
Erika Moore, MD; Darshan Roy, MD; Patti Cohen, MD; Adam Bagg, MD
October 24th, 2013

2. Clinical History
36-year-old woman was admitted for a cesarean section and immediately post-operatively developed a fever
Received two-day course of antibiotics for presumed endometritis
She had persistent fevers and was admitted two weeks later for a clinical work-up
Peripheral smear reportedly reviewed by hematology-oncology and interpreted as having “atypical lymphocytes with some blast-like cells that look more viral/reactive than malignant”
Discharged after an extensive infectious disease work-up failed to reveal a source of the fevers
Re-admitted a week later with persistent fevers
CBC was significant for progressive cytopenias
Peripheral blood sent for flow cytometry and a bone marrow biopsy was performed.

3. Peripheral Blood Flow Cytometry
CD79a
Tdt
SSC-A
CD45
CD34
CD10
CD19
CD5
MPO
Tdt
This was signed out as B-cell ALL. There was mention of heterogenous expression of CD13 (which I haven’t shown you) but no other myeloid marker expression and you can see MPO is negative
CD34+ CD10(subset)+ CD19+ TdT+ CD79a+ MPO- lymphoblasts

4. Cellularity is almost 100% , very monotonous on low power without normal cell architecture

5. Blasts comprise the majority of cells
Majority of cells are immature precursors ranging in in size from small/medium to large

6. Morphologic spectrum of blasts Larger blasts are MPO+ SBB+
50x
50X
MPO 100x
MPO+ blasts
MPO- blasts
Larger blasts are MPO+ SBB+
SBB 100x
SBB-blast
SBB+blast
Spectrum of blast types, are smaller blasts with scant cytoplasm to large blasts with relatively abundant cytoplasm; but not a definite dimorphic population, larger blasts are positive for MPO and Sudan black b, while smaller blasts are negative

7. Blasts express myeloid and lymphoid markers
CD10
MPO
Returning to the trephine, immunostains demonstrate expresion of both myeloid and lymphoid markers with diffuse positivity for CD10, subset positivity for MPO, TdT and CD15
TdT
CD15

8. Smaller lymphoid blasts and larger myeloid blasts
CD79a
MPO
On higher power, I think you can appreciate again that the smaller blasts are staining with Cd79a while the larger blasts are positive for MPO
CD79a
MPO

9. Bone Marrow Aspirate Flow Cytometry: Two Populations?
CD34+ CD10 (subset)+ CD20- CD19+ CD13+CD33(subset)+ myeloblasts
CD10
CD34
CD19
CD20
CD33
CD13
myeloblasts
CD45
lymphoblasts
CD10
CD34
CD19
CD20
CD13
CD33
Flow cytometry performed on the bone marrow demonstrated two blast populations with different immunophenotypes, a myeloblast population which is Cd34, Cd10 subset, Cd19+, cD13+ and CD33 subset + and a B-lymphoblast population that is CD34+ CD10+ CD19+ CD13+ and CD33-
SSC-A
CD34+ CD10(subset)+ CD19+ CD13+ CD33- lymphoblasts

10. Bone Marrow Aspirate Flow Cytometry: Two Populations?
TdT(subset)+ MPO+ CD79a(subset)+ myeloblasts
myeloblasts
Tdt
Tdt
CD45
MPO
CD79a
lymphoblasts
Looking at Tdt, MPO, and CD79a, the myeloblast population is MPO+ and mostly TdT and CD79a neg with a small subset positive for both Tdt and CD79a The lymphoblast population is Tdt and CD79a+ and MPO-
Tdt
Tdt
SSC-A
CD79a
MPO
TdT+ MPO- CD79a+ lymphoblasts

11. Bone Marrow Aspirate Flow Cytometry: One Population?
SSC-W
CD45
[Leukocytes]
CD3
CD79a
[Blasts, T, & B cells]
Neutrophils
Monocytes
Lymphocytes
Blasts
CD34+ Blasts
CD10
CD34
[Myeloid & B] cells]
CD3
MPO
[Blasts & T cells]
Mostly a myeloblastic mixed lineage population expressing CD34, CD13, low MPO, CD19, cCD79a and CD10
Courtesy of Dr. Portwit & Dr. Bene

12. FISH showed +BCR-ABL1 translocation in 156/200 cells (78%)
Negative FISH
Positive FISH

13. Mixed phenotype acute leukemia (B/myeloid) with t(9;22)(q34;q11.2)

14. Interesting Features Biphenotypic versus bilineal
Different composition of blasts circulating in the peripheral blood than those found in the bone marrow

15. Bilineal or Biphenotypic?
Distinct blast populations, each of a different lineage
Biphenotypic
One population of blasts expressing antigens of different lineages on the same cells
MPAL as defined by 2008 WHO encompasses bilineal and biphenotypic leukemias, as well as a combination.

16. Bilineal, Biphenotypic, or Both?
Myeloid Lineage
B Lineage
-MPO
-Monocytic differentiation (2: NSE, CD11c, CD14, CD64, lysozyme)
-Strong CD19 & strong CD79a, cCD22, CD10
-Weak CD19 & 2 strong
BM Myeloblasts BM
B-Lymphoblasts
CD34 +
CD4 -
CD10
+ (var)
CD13
CD15
CD19
CD33
CD79a
HLA-DR
Tdt
MPO
Bilineal
Two blast populations
B-lymphoid
Myeloid
Biphenotypic
Lineage “infidelity” within each blast population
Myeloblasts express CD10, CD19, CD79a, and TdT
B lymphoblasts express CD13
Each individual population on it’s own would not meet criteria for biphenotypic leukemia

17. Interesting Features Biphenotypic versus bilineal
Different composition of blasts circulating in the peripheral blood than those found in the bone marrow

18. Blast Antigen Expression by Population
BM Myeloblasts
BM Lymphoblasts
Peripheral Blood
CD34 +
CD4 -
CD10
+ (var)
CD13
+(var)
CD15
CD19
CD33
CD79a
HLA-DR
Tdt
MPO

19. Discrepant immunophenotype at different locations
Described in lymphomas
Tissue microenvironment may alter antigen expression
One report of immunophenotypic discrepancy in acute leukemia (2 cases of MPAL)
Patient 1: CD3+ Tdt+ in lymph node but negative in bone marrow
Patient 2: MPO+ in lymph node but negative in bone marrow
Korean J Lab Med 2009
Song et al. Korean J Lab Med 2009; 29:

20. Survival Difference in MPAL
ALL (n=101)
AML (n=191)
BAL (n=21)
St Jude
Rubnitz et al. Blood 2009; 113:
Shanghai
Xu et al. Haematologica 2009

21. Blood 2011
Ph+
Blood 2011; 117:

22. Follow-Up
Received chemotherapy and subsequently underwent an allogeneic stem cell transplant
Post-transplant chimerism analysis of the peripheral blood shows >99% donor cells
She has remained disease free for 2 years and had a recent negative RT-PCR for BCR-ABL1 fusion mRNA
Currently on dasatinib