Submitting Author: Leventaki, Vasiliki, MD
Institution: The University of Texas MD Anderson Cancer Center
Additional authors:Weina Chen, MD, PhD, Carlos Bueso-Ramos MD, PhD
Session: AML with myelodysplasia-related changes

A 60-year-old woman in her usual state of health presenting with low-grade fever, shortness of breath and dyspnea on exertion since October 2012. On 01/07/13, a complete blood count (CBC) was performed at an outside institution that showed a white blood cell count (WBC) of 4.2 K/uL, with an absolute neutrophil count 280/uL, hemoglobin (Hb) 7.7 g/dL, and platelet count (PLT) over 1,000 K/uL. The patient was admitted to an outside hospital and received blood transfusion. A bone marrow evaluation was performed that showed acute leukemia. The patient was referred to our institution for further evaluation. At the time of admission, the CBC count showed WBC 2.9 K/uL, Hb 8.1g/dL, PLT 1069 K/uL, and circulating blasts 35%. Physical examination did not show hepatosplenomegaly. Bone marrow biopsy confirmed the diagnosis of acute myeloid leukemia with 23% blasts and the patient was scheduled to receive chemotherapy (Clofarabine, Idarubicin and Cytarabine) and reduced intensity allogeneic stem cell transplant

Bone marrow smears, and formalin-fixed paraffin-embedded clot and bone marrow core biopsy sections, and peripheral blood smear.

Peripheral blood smear showed increased blasts (35%) that were large in size with scant to moderate cytoplasm. No Auer rods were identified. There was marked thrombocytosis including giant platelets and platelet clumps.

Bone marrow smears were adequate for evaluation and showed 23% blasts with trilineage dysplasia. Bone marrow core biopsy was limited for evaluation and showed hypercellular bone marrow (95%) with sheets of immature cells. Megakaryocytes were increased (up to 25 per high-power field) and dysplastic with hypolobated forms, focally forming clusters. Clot sections showed similar morphologic findings to that described in the bone marrow biopsy.

Special stains performed on the bone marrow biopsy for reticulin showed a slight increased and loose of reticulin network. Trichrome stain was negative for the presence of collagen fibers. The fibrosis grading was MF-1 based on the European Myelofibrosis Network.

Blasts were positive for myeloperoxidase (27%) and negative for butyrate esterase by cytochemical stains. Iron stain on aspirate smear showed increased iron stores (3+ in a scale of 0-4+), increased sideroblastic iron incorporation and 51% ring sideroblasts.

Immunohistochemical studies performed on the bone marrow biopsy showed that the blasts were negative for CD34 and CD61. Approximately 25% of the blast cells show nuclear staining for the p53 stain. The CD61 stain also highlights the scattered megakaryocytes.

Flow cytometric analysis performed on the bone marrow aspirate specimen showed CD45dim blast population (50%) that was:

• positive for CD13, partial CD33, partial CD34, partial CD38, CD49d, partial CD42b, CD117, CD123, and small subset for myeloperoxidase and

• negative for CD2, CD4, CD5, CD7, CD10, CD14, CD15, CD19, CD22, CD36, CD41, CD56, CD61, CD64, HLA-DR

Conventional cytogenetic studies performed on the bone marrow aspirate specimen showed female hyperdiploid karyotype with trisomy 15, 46, XX, +15.

Gene mutation analysis performed on the bone marrow aspirate specimen showed:

• DNMT3A gene mutation in codon 882, exon 23 (CGC to CAC)

• IDH2 gene mutation in codon 140, exon 4 (CGG to CAG)

• Negative mutation analysis for: KRAS, NRAS, NPM1 (exon12), IDH1 (R132), KIT (exon 17), FLT3 (IDT), FLT3 (codons 835/836), CEBPA and TP53.

Negative for the presence of fusion transcripts assessed by real-time PCR:

• BCR-ABL/ t(9;22)(q34;q11), including b3a2, b2a2 and e1a2

• PML-RARA/t(15;17)(q22;q21), transcripts of the short and long forms

• CBFb-MYH11/inv(16), A and D forms

• AML1-ETO/t(8;21)(q22;q22)

• E2A-PBX-1/t(1;19)(q23;p13)

• MLL-AF4/t(4;11)(q12;q23)

• TEL-AML1/t(12;21)(p12;q22)

This is an uncommon presentation of de novo acute myeloid leukemia with marked thrombocytosis and no prior history of myeloproliferative or myeloproliferative/myelodysplastic neoplasm. The main diagnostic consideration includes acute myeloid leukemia with inv(3) or t(3;3) that involves the oncogene EVI1 at 3q26.2 and may present de novo or arise from a prior myelodysplastic syndrome. They are often associated with elevated platelet count and increased predominantly small megakaryocytes in the bone marrow and trilineage dysplasia. In our case, the megakaryocytes were increased but included both small and large forms and cytogenetic studies did not show chromosome 3 abnormalities. Evaluation for the expression of megakaryocytic markers (CD41, CD42b, CD61, CD36) by flow cytometry on the blasts only showed partial CD42b expression. Megakaryocytic differentiation could not be convincingly supported in this case due to the markedly increased number of platelets that can bind to blast and create an artificially positive signal. Extensive gene mutation analysis identified mutations in DNMT3 located at 20q11.21 and IDH2 located at 15q26. The detection of the latter mutation along with the presence of clone with an extra copy of chromosome 15, where the IDH2 is located, is of uncertain significance. Also, the current published data are inconclusive regarding the prognostic impact of these mutations in AML. A recent study reported no significant impact of DNMT3 or IDH1/2 mutations on overall survival (Grossmann et al Blood 2012; 120:2963-2972). An additional interesting finding is the detection of p53 protein expression on a subset of the blast population in the absence of TP53 mutation, suggesting an alternative mechanisms of p53 deregulation possible mediated by the two major p53 regulators, mdm2 and mdm4.

Acute myeloid leukemia with trilineage dysplasia and thrombocytosis without prior history of myelodysplastic and/or myeloproliferative neoplasm.

Acute myeloid leukemia with myelodysplasia-related changes, with marked thrombocytosis, with IDH2 mutation and DNMT3A mutation

Case 319