ICCS e-Newsletter CSI Fall 2010 David D. Grier, M.D. Department of Pathology. Wake Forest University

e-CSI - Clinical History: 61 year old man with no significant past medical history presented to his primary care physician complaining of fatigue, easy bruising, mild dyspnea on exertion, and headache for 3 weeks.

e-CSI - Peripheral Blood: CBCNormal Range –WBC: 24.0 x 10 9 /l (4.8 – 10.8) –RBC:3.51 x /l (4.7 – 6.1) –Hgb: 11.2 g/dl (14.0 – 18.0) –Hct: 31.5 % (42.0 – 52.0) –MCV:89.8 fl (80.0 – 94.0) –MCH: 32.0 pg (27.0 – 31.0) –MCHC: 35.6 g/dl (33.0 – 37.0) –RDW: 15.4% (11.5 – 14.5) –Plts: 19.0 x 10 9 /l (160 – 360)

e-CSI - Peripheral Blood: CBC Differential –Granulocytes:11% –Bands:1% –Lymphocytes: 6% –Monocytes:1% –Basophils:2% –Eosinophils:0% –Blasts/Promyelocytes: 72%

e-CSI – Clinical History Bone marrow aspirate and biopsy were received for evaluation. Flow cytometric immunophenotyping was performed on a portion of the bone marrow aspirate and the results from selected 3-color and 5-color tubes are provided for review.

e-CSI - Flow Cytometric Studies Acquired with a FC500 and initially analyzed with CXP Analysis 2.0 and then with FSC Express version 3 Tube 1: CD34~FITC/ CD2~PE/ CD117~PC5/ CD45~PC7 Tube 2: CD7~FITC/ CD33~PE/ CD45~PC7 Tube 3: HLA-DR~FITC/ CD13~PE/ CD45~PC7

e-CSI - Flow Cytometric Analysis Large population of atypical cells with increased side scatter. There are very few events in the “blast gate”.

e-CSI - Flow Cytometric Analysis The atypical cell population has uniform expression of CD33

e-CSI - Flow Cytometric Analysis There is no expression of HLA-DR and variable expression of CD13.

e-CSI - Flow Cytometric Analysis There is expression of CD2 and CD34.

e-CSI – Key immunophenotypic findings The atypical cells have high side scatter and fall in the “myeloid gate”. Few events are seen in the “blast gate”. The cells express CD34, CD117, and CD2. CD13 expression is heterogenous. CD33 expression is homogenous. There is no expression of HLA-DR.

Numerous atypical cells were seen. The nuclei were indented and overlapping. Few cytoplasmic granules were seen. No Auer rods were identified.

The bone marrow core biopsy was 100% cellular with the marrow space almost completely replaced by blasts.

Molecular cytogenetic analysis with DNA probes specific for the 15;17 translocation [PML-15q22 and RARA-17q21] was performed and revealed that a total of 82.5% of the interphase nuclei had a PML/RARA fusion event. Two fused signals, one red and one green, indicating the fused PML-RARA (yellow).

e-CSI Fall 2010– Diagnosis Acute promyelocytic leukemia (APL), microgranular variant (Acute myeloid leukemia with t(15;17)(q22;q12)).

e-CSI – APL characteristic immunophenotype Absent or low expression of HLA-DR, CD34, CD11a, CD11b, CD15, and CD64. Homogenous expression of CD33 Heterogenous expression of CD13 Expression of CD117, but it may be weak. CD56 is seen in approximately 20% of cases.

e-CSI – APL characteristic immunophenotype Strong myeloperoxidase expression. Microgranular variant can express CD34 and CD2. By CD45/side scatter the leukemic cells are typical found in the “myeloid gate”. Occasionally there is a “hockey stick” configuration. Microgranular variant tends to have lower side scatter.

e-CSI – APL characteristic immunophenotype Lack of HLA-DR and CD34 is not specific for APL and can be seen in other types of acute myeloid leukemia. Immunophenotyping can suggest a diagnosis of APL, but it is NOT diagnostic.

e-CSI – APL clinical presentation Fatigue, weakness, and dyspnea related to anemia. Easy bruising or bleeding caused by thrombocytopenia or coagulopathy. Most cases present with pancytopenia. –Microgranular variant can have very high WBC counts. Risk of disseminated coagulopathy.

e-CSI – APL Diagnosis Suspicion for APL is typically raised by morphologic assessment. –Abnormal promyelocyte morphology –Abundant cytoplasmic granules –Microgranular/hypogranular variant can have few to no visible granules. –Frequent Auer rods –Irregular nuclei: bilobed and kidney shaped. More frequently seen in microgranular variant. The diagnosis is confirmed by cytogenetics (FISH).

e-CSI – APL Differential diagnosis Acute myeloid leukemia –HLA-DR negative leukemia is not limited to APL –Cytogenetics essential for diagnosis –APL is sometimes mistaken, especially the microgranular variant, for monocytic leukemia due to the nuclear features Growth factor effect –Lower blast counts –Lacks atypical nuclei –No t(15;17) abnormality

e-CSI – APL Treatment The correct diagnosis is essential since the treatment is very different from other types of AML. Treatment consists of all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy for induction and ATRA plus arsenic trioxide for consolidation. Some cytogenetic variants are ATRA resistant. –ZBTB16 (11q23), STAT5B (17q11.2)

e-CSI – references Nagendra S, Meyerson H, Skallerud G, et al. Leukemias resembling acute promyelocytic leukemia, microgranular variant. American journal of clinical pathology 2002:117(4): Orfao A, Chillon MC, Bortoluci AM, et al. The flow cytometric pattern of CD34, CD15 and CD13 expression in acute myeloblastic leukemia is highly characteristic of the presence of PML-RARalpha gene rearrangements. Haematologica 1999:84(5): Redner RL. Variations on a theme: the alternate translocations in APL. Leukemia 2002:16(10):