1. Julia Geyer and Attilio Orazi
2013 SH/EAHP Workshop Case 185
Julia Geyer and Attilio Orazi

2. Clinical information
72 year old man diagnosed with essential thrombocythemia (ET) in 2001 (slides not available for review)
At the time of diagnosis the platelet count was 1.2 x 106/L and the clinical picture was complicated by a transient ischemic attack
Treated with Anagrelide and Hydroxyurea until October 2009 when he developed anemia and became transfusion-dependent

3. Clinical information
A bone marrow biopsy (BM) performed in 12/2009 showed evidence of a chronic myeloproliferative neoplasm (MPN) with 1 to 2+ reticulin fibrosis and no increase in blasts
BM performed in 02/2010 showed increased fibrosis and 10% blasts by flow cytometry (unclear if peripheral blood contamination)
The patient was treated with 4 cycles of decitabine
BM in 05/2010 reported a markedly hypocellular bone marrow with 1+ fibrosis and without increased blasts

4. Clinical information
The patient did well for 6 months until he again became transfusion-dependent in 11/2010
BM showed accelerated phase MPN with 16% blasts and 3+ reticulin fibrosis
Treated with an investigational drug TG02 (oral multi-kinase inhibitor), however he remained transfusion-dependent and had detectable circulating blasts in peripheral blood (1-9% of all cells)
BM in 07/2011 showed 15% blasts, 3+ fibrosis and a new cytogenetic abnormality

5. Clinical information
In September 2011, the patient was admitted due to acute renal insufficiency and altered mental status
BM showed 24% blasts
Treated with 7+3 induction regimen, complicated by tumor lysis syndrome, worsening renal failure, respiratory failure and sepsis
The patient passed away in 11/2011
10 years after initial diagnosis of ET, 21 months after diagnosis of accelerated phase MPN and 2 months after diagnosis of blast phase MPN

10. CD42b

11. CD61

12. CD117

13. Immunohistochemistry
An increased number of CD34(-), CD117(+) myeloid blasts
MPO highlighted rare left-shifted myeloid cells
Glycophorin C was positive in rare scattered erythroid cells
CD42b and CD61 highlighted a marked increase in the number of megakaryocytes, micromegakaryocytes and megakaryoblasts
These cells focally form large aggregates
TdT, CD56 and CD99 were negative

14. Flow cytometry
Increased number of blasts that expressed CD34 (dim), CD117, CD13, CD33, HLA-DR, CD36, CD56 and CD41

15. Molecular and cytogenetic analysis
Negative for JAK2, FLT3, NPM1 and CEBPA mutations
Normal male karyotype 46,XY
July 2011, new translocation: 46,XY,der(6)t(1;6)(q21;p21)
8 months following diagnosis of accelerated phase and 2 months prior to diagnosis of blast phase MPN

16. Proposed diagnosis
Myelofibrotic myeloproliferative neoplasm, megakaryoblastic blast phase
Consensus diagnosis
Myeloproliferative neoplasm with myelofibrosis [post ET vs. PMF], accelerated phase progressing to megakaryoblastic blast phase

17. Interesting features of the case
Disease progression is uncommon in patients with essential thrombocythemia
Since we did not have the opportunity to review the patient’s diagnostic BM, there is a possibility that based on the WHO criteria the correct initial diagnosis was that of early primary myelofibrosis with thrombocytosis

18. Interesting features of the case: unique cytogenetic abnormality
Unlike CML, other MPNs have no specific cytogenetic abnormalities
Recurrent abnormalities are seen in ~30% of PMF patients and 5-10% of ET patients at diagnosis; this proportion increases with time after diagnosis (up to 40% of post-ET MF patients)
The type of cytogenetic abnormalities seen in PMF, PV, post-PV MF and post-ET MF is similar
The most frequent abnormalities are del(20q), del(13q), +8, +9, and abnormalities of chromosomes 1 and 7
Hussein K, et al. Eur J Haematol 2009
Tefferi A, et al. Br J Haematol 2001

19. Initially identified in 3/81 patients with PMF
Subsequent cytogenetic database search identified additional 14/25791 patients
All patients had features typical of myelofibrosis
10/14 patients had PMF
3/14 patients had post-PV MF
1/14 patient had post-ET MF
Median survival was 7.8 years
Only 1 patient progressed to AML

20. Interesting features of the case: unique cytogenetic abnormality
Translocation t(1;6)(q21;p21) appears to be highly specific to patients with myelofibrosis
Likely a naturally occurring genetic signature of the disease and not a consequence of exposure to cytotoxic therapy or marker of disease transformation
In this particular case, it was acquired in the course of disease progression from accelerated phase to the blast phase
22 cases with sole 13q or 20q
abnormalities showed superior prognosis than the 58
cases with cytogenetic abnormalities other than 13q
and 20q but not than patients with a nor-
mal karyotype
Dingli D et al, Br J Haematol 2005
Zamecnikova A. Atlas Genet Cytogenet Oncol Haematol 2011

21. Interesting features of the case: megakaryoblastic transformation
While de novo acute megakaryoblastic leukemia is very rare, megakaryoblastic transformation of myeloproliferative neoplasms likely occurs more frequently
Hernandez and colleagues reported 3/9 cases of blast phase MPN had megakaryoblastic proliferation
Megakaryoblasts are medium-sized to large cells with dense chromatin and scant to moderately abundant cytoplasm, often with irregular borders and projections (blebbing)
Some cases have lymphoblast-like appearance
Identified by their flow cytometric characteristics and/or by their immunohistochemical reactivity with CD41, CD42b, CD61, CD31 and vWF
Micromegakaryocytes (cell diameter <15 mm) are small nonlobulated megakaryocytes with a lower nuclear:cytoplasmic ratio and more abundant cytoplasm than megakaryoblasts
Hernandez JM et al, J Clin Pathol 1992
Georgii A et al, Leuk Lymphoma 1996
Vianelli N et al, Haematologica 1996
Orazi A et al, Mod Pathol 2005

22. Acute megakaryoblastic leukemia
Associated with Down syndrome
>50% of AML in these patients is megakaryoblastic
Majority of cases occur in children <5 years
Erythropoiesis and granulopoiesis are frequently dysplastic and fibrosis is common
Somatic mutation of GATA1 is pathognomonic
Associated with t(1;22)(p13;q13); RBM15-MKL1
Young children, typically without Down syndrome
Marked organomegaly
Fibrosis, but no evidence of erythroid or myeloid dysplasia
Associated with AML, NOS
Both adults and children
No unique chromosomal or genetic abnormalities