Submitting Author: Chen, Dong, MD,PhD
Institution: Mayo Clinic
Additional authors:James D. Hoyer,MD
Session: AML secondary to myeloproliferative neoplasms and other types of disease progression in MPN

60 year old man was found to have elevated CBC (platelets of 711, hemoglobin of 17.5, white count of 16.5.) in 2008. His bone marrow biopsy was consistent with MPN unclassifiable. JAK2 V617F on peripheral blood was positive. He was then managed with hydroxyurea for 2 years.

In 2011, he developed pancytopenia and a bone marrow biopsy and aspirate was performed (the submitted case).

Patient died 3 months later at the age of 63.

Tissue Description:

Peripheral Blood

CBC (dated 9/1/11): Hgb 8.6 g/dL; RBC 3.01 x 10(12)/L; MCV 85.7 fL; RDW 16.2%; WBC 2.2 x 10(9)/L; PLT 10 x 10(9)/L.

White blood cell differential: neutrophils 43%; lymphocytes 27%; monocytes 12%; eosinophils 1%; basophils 2%; metamyelocytes 1%; myelocytes 6%; blasts 8%; megakaryocytes/megakaryoblasts 6%.

Peripheral smear: Pancytopenia.

Red blood cells: Slight anisopoikilocytosis with slightly increased elliptocytes and no dacrocytes or schistocytes.

White blood cells: Left-shifted granulocytic precursors, including 8% circulating myeloblasts and megakaryoblasts. There are also circulating megakaryocyte nuclei. There is a rare hypogranular neutrophil.

Platelets: Large, hypogranular platelets present.

Bone Marrow Aspirate/Touch Imprint

Quality: Hemodilute and without units. The cellularity present generally reflects peripheral blood contamination. There are rare megakaryoblasts.

Bone Marrow Biopsy/Clot

Quality: Adequate for evaluation.

Cellularity: Densely fibrotic with dilated sinusoids and some increase in bony trabeculae.

Erythroid precursors: Markedly decreased.

Granulocytic precursors: Markedly decreased.

Megakaryocytes: Markedly Increased and atypical with focal clustering and sheets. There are both small monolobate and larger osteoclast-like forms present.

Lymphocytes: No lymphoid aggregates.

Plasma cells: Decreased.

Reticulin stain, bone marrow biopsy: Reticulin fibers are markedly increased, grade 3+.

Immunohistochemical studies, bone marrow biopsy, antibodies to CD3, CD20, CD34, CD61, hemoglobin, myeloperoxidase, VWF: Antihemoglobin shows a virtual absence of erythroid precursors. Myeloperoxidase shows scattered, left-shifted granulocytic precursors. There is a slight increase in small CD20-positive B-cells and a normal population of small CD3-positive T-cells. Virtually the entire immature population, as well as the atypical megakaryocytes, are positive for the markers VWF and CD61. These cells are negative for CD34.

Flow cytometric immunophenotyping, bone marrow aspirate:

1. Blasts: Increased, 17% (CD45/light scatter); express CD13 (dim), CD33 (dim), CD117 (dim), CD7; do not express CD34, HLA-DR, CD10, CD19.

2. B-cells: No monotypic.

3. T-cells: No increase in aberrant CD3/CD16-positive T-cells or increase in natural killer (NK)-cells.

Flow analysis with antibodies to the following antigens:

Triage panel: CD3, CD10, CD16, CD19, CD45, and kappa and lambda surface immunoglobulin light chains.

Acute panel: CD2, CD3, CD5, CD7, CD10, CD13, CD15, CD19, CD20, CD33, CD34, CD56, CD117, and HLA-DR.

Cytogenetic studies on bone marrow aspirate:

46,XY[20]

AML FISH studies on bone marrow aspirate:

inv(3)(RPN1/EVI1) normal

-5 normal

5q- normal

t(6;9)(DEK/CAN) normal

-7 normal

7q- normal

t(8;16)(MYST3/CREBBP) normal

t(8;21)(ETO/AML1) normal

+8(D8Z2/MYC) normal

t(9;22)(BCR/ABL) normal

11q23(MLL sep) normal

13q- normal

t(15;17)(PML/RARA) normal

inv(16)(MYH11/CBFb) normal

20q- normal

Peripheral blood, JAK2 V617F mutation analysis: Positive.

JAK2 V617F mutated DNA was detected and measured at 0.4% of total JAK2 DNA.

Acute megakaryoblastic leukemia (AML-M7) is the most comment type of transformation in patients with MPN (1).

However the peripheral blood and bone marrow aspirate smear are frequently very pancytopenic and sparsely cellular, respectively. The markedly increased small and dysplastic megakaryocytes are common features in end stage MPN. Since megakaryoblasts count can not be reliably assess on peripheral bone marrow aspirate due to marked fibrosis, there is no dependable criteria for diagnosing AML-M7 on bone marrow biopsy in such a patient population.

1: Mesa RA, Li CY, Ketterling RP, Schroeder GS, Knudson RA, Tefferi A. Leukemic transformation in myelofibrosis with myeloid metaplasia: a single-institution experience with 91 cases. Blood. 2005 Feb 1;105(3):973-7.

Acute megakaryoblastic leukemia transformation from patient’s pre-existing MPN.

Myeloproliferative neoplasm, unclassifiable, JAK2 mutation positive, in accelerated phase (megakaryocytic/megakaryoblastic progression)

Case 70