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
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.
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
Cellularity is almost 100% , very monotonous on low power without normal cell architecture
Blasts comprise the majority of cells Majority of cells are immature precursors ranging in in size from small/medium to large
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
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
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
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
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
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
FISH showed +BCR-ABL1 translocation in 156/200 cells (78%) Negative FISH Positive FISH
Mixed phenotype acute leukemia (B/myeloid) with t(9;22)(q34;q11.2)
Interesting Features Biphenotypic versus bilineal Different composition of blasts circulating in the peripheral blood than those found in the bone marrow
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.
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
Interesting Features Biphenotypic versus bilineal Different composition of blasts circulating in the peripheral blood than those found in the bone marrow
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
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: 396-401
Survival Difference in MPAL ALL (n=101) AML (n=191) BAL (n=21) St Jude Rubnitz et al. Blood 2009; 113: 5083-5089 Shanghai Xu et al. Haematologica 2009
Blood 2011 Ph+ Blood 2011; 117: 3163-3171
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