Submitting Author: Lu, Gary, MD
Institution: UT MD Anderson Cancer Center
Additional authors:Roger A. Schulz, Carlos E. Bueso-Ramos, Jorge E. Cortes, Xiaohong Iris Wang, L. Jeffrey Medeiros, C. Cameron Yin
Session: AML with recurrent genetic mutations Part II

The patient was a 68-year-old man who presented with worsening shortness of breath, fever, and an elevated white blood count (WBC) in August 2011. A complete blood cell count showed WBC 101.7 K/uL, hemoglobin 9.3 g/dL, platelet count 22 K/uL, with 64% blasts. A bone marrow (BM) biopsy revealed a hypercellular bone marrow with sheets of myeloblasts. A diagnosis of acute myelomonocytic leukemia was made, with diploid karyotype and mutations in FLT3 (ITD) and NPM1 genes. The patient was treated with Vidaza and Sorafenib, and achieved complete morphologic remission, with low-level FLT3-ITD detected by polymerase chain reaction. The patient then underwent an allogeneic stem cell transplant (ASCT) on 1/25/2012, and achieved complete morphologic and molecular remission in one month.

On 3/29/2012, cytogenetic analysis detected an abnormal clone showing isolated t(12;13)(p13;q12) in 2 of 20 metaphases. FISH study with dual color fusion break apart probe confirmed EVT6 rearrangement in 12p13 region. A modified translocation comparative genomic hybridization array (tCGH) confirmed FLT3/ETV6 gene fusion. Bone marrow evaluation showed slightly increased (5%) blasts, indicating relapsing disease. The clone carrying t(12;13) expended rapidly in the BM showing an isolated t(12;13)(p13;q12) in all 20 metaphase cells in 12 days. The disease then progressed rapidly showing 45% blasts in the BM on 4/10/2012. The patient expired on 4/13/2012, only 15 days after the first detection of the t(12;13)(p13;q12) clone at relapse. The overall survival of the patient was less than 8 months.

At initial diagnosis, BM biopsy demonstrates a hypercellular (90%) BM with trilineage hypoplasia and sheet of immature cells. The BM aspirate smear shows increased blasts with irregular nuclei, fine chromatin, prominent nucleoli, and occasional cytoplasmic vacuolation.

At initial diagnosis, flow cytometry revealed a distinct population of blasts that were positive for CD13, CD33, CD49d, CD64 (dim), CD117, CD123, CD184, HLA-DR, myeloperoxidase, and TdT (subset), and were negative for CD14, CD19, CD34, CD56, consistent with myeloid immunophenotype.

Immunohistochemistry staining using phospho FLT3 antibody on BM biopsy at relapse revealed positive result on immature cells and blasts, indicating FLT3 over-expression and phosphorylation.

At initial diagnosis, conventional cytogenetic study revealed 46,XY[20].

On 3/29/2012, cytogenetic analysis detected an abnormal clone showing isolated t(12;13)(p13;q12) in 2 of 20 metaphases. FISH study with dual color fusion break apart probe confirmed EVT6 rearrangement at 12p13 region. A modified form of oligonucleotide-based tCGH designed to detect balanced translocations confirmed the presence of FLT3/ETV6 gene fusion due to the t(12;13).

The clone carrying t(12;13) expended rapidly in the BM showing an isolated t(12;13)(p13;q12) in all 20 metaphase cells on 4/10/2012.

Molecular testing at initial diagnosis showed mutations in both FLT3 (internal tandem duplication, ITD) and NPM1 (4 base pair insertion in exon 12) genes. No mutation was detected in KRAS, NRAS, KIT, CEBPA, IDH1 and IDH2 genes. A multiprobe-bead array assay did not detect any of the fusion transcripts for BCR-ABL1/t(9;22)(q34;q11.2), PML-RARA/t(15;17)(q24;q21), the A and D forms of CBFB-MYH11/inv(16)(p13.1q22), RUNX1-RUNX1T1/t(8;21)(q22;q22), E2A-PBX1/t(1;19)(q23;p13.3), MLL-AF4/t(4;11)(q21;q23) and ETV6-RUNX1/t(12;21)(p13;q22).

On 3/29/2012, mutational analyses for both FLT3 and NPM1 were negative. FLT3-ITD was detected at the patient's last BM biopsy collected on 4/10/2012.

We present a fatally progressive case of AML with FLT3-ITD as the first pathogenic event followed by FLT3/ETV6 fusion leading to FLT3 over-expression, which is generated by an isolated t(12;13)(p13;q12).

Acute myeloid leuekemia with double-hit genetic abnormalities of the FLT3 gene

Acute myeloid leukemia with t(12;13)(p13;q12);FLT3/ETV6, with additional FLT3 ITD mutation and NPM1 mutation

Case 360