1. Hemophagocytic Lymphohistiocytosis Associated with Acute Myeloid Leukemia with RUNX1-RUNX1T1 Fusion
Adam J. Wood, D.O.
Rhett P. Ketterling, M.D.
April E. Chiu, M.D.
Kaaren K. Reichard, M.D.
Mayo Clinic, Rochester, MN

2. Clinical History
26-year-old male in good health prior to 2/2015 when he presented with constitutional symptoms:
Fevers
Nausea
Vomiting
Weakness with ↓ energy
Night sweats
50 lb. weight loss

3. Clinical History Con’t
2/2015
4/2015
9/2015
Blood Chemistries (normal values)
AST (8-48) U/L
1017
3158
1176
ALT (7-55) U/L
909
1039
579
Alk phos (45-115) U/L
182
508
338
Tbili (≤1.2) md/dL
0.5
6.7
1.8
CBC (normal values)
Hgb ( ) mg/dL
14.2
WBC ( ) x 109/L
1.1
1.3
ANC ( ) x 109/L
0.55
0.37
PLTS ( ) x 109/L 82
197
130
•↑ LFTs •Cytopenias •↑ ferritin (7614 μg/L)

4. Clinical History Con’t
Gastrointestinal work-up:
Biochemical abnormalities suggestive of Wilson’s disease
No Kayser-Fleischer rings
Liver biopsies did not reveal copper accumulation
Negative infectious disease work-up
Negative CT imaging with no significant lymphadenopathy

5. Clinical History Con’t
10/2015: Hematology suggested bone marrow (BM) biopsy due to 8 months of persistent unexplained constitutional symptoms & cytopenias

6. Morphologic Findings-Peripheral Blood
CBC: pancytopenia
Hgb 12.7 g/dL
RBC 4.21 x 1012/L
MCV 88.1 fL
RDW 17.7%
WBC 0.6 x 109/L
PLT 98 x 109/L
Smear: rare circulating tumor cell (inset)

7. Morphologic Findings-BM Aspirate
Markedly ↑ BM histiocytes

8. Morphologic Findings-BM Aspirate Con’t
Marked hemophagocytosis

9. Morphologic Findings-BM Aspirate Con’t
Scattered atypical tumor cells

10. Morphologic Findings-BM Aspirate Con’t
Very rare single, thin, Auer rod identified

11. Morphologic Findings-BM Aspirate Con’t
Morphologic spectrum of tumor cells, with (A, B) & without (C, D) Auer rods

12. Morphologic Findings-BM Aspirate Con’t
Normal (A) & atypical (B-D) megakaryocytes

13. Morphologic Findings-BM Biopsy
CD34
Hypocellular with panhypoplasia
↑ CD34+ blasts (20-30%) differentially distributed in the interstitium

14. Morphologic Findings-BM Biopsy Con’t
Blasts with notched nuclei, stippled chromatin & mitosis

15. Morphologic Findings-BM Biopsy Con’t
CD68
Markedly ↑ hemophagocytic histiocytes

16. Morphologic Findings-BM Biopsy Con’t
CD61
No significant population of small, atypical megakaryocytes

17. ↑ population of CD34+ blasts
Immunophenotype
↑ population of CD34+ blasts

18. Immunophenotype Con’t
Blasts express: CD34, CD45 (dim), CD13 (dim), CD33, CD117, HLA-DR, CD7 (partial), CD56 & CD38

19. Cytogenetics-Conventional Chromosome Study
Normal

20. Cytogenetics-FISH
Within normal limits for KAT6A (MYST3) & CREBBP gene regions
Within normal limits for PML & RARA gene regions

21. Cytogenetics-FISH Con’t
RUNX1T1-RUNX1 fusion in 47% of interphase nuclei
Normal FISH result on multiple normal metaphases

22. Molecular Studies PML-RARA mRNA analysis, peripheral blood: Negative
Next generation sequencing results, bone marrow: WT1: c.938dup; p.Ala314Glyfs*3 (10%)

23. Proposed Diagnosis
Hemophagocytic lymphohistiocytosis with acute myeloid leukemia with RUNX1-RUNX1T1 fusion & normal karyotype

24. Follow Up
Further investigation into the patients PMHx revealed a BM biopsy was performed 4/7/15:
Low normal cellular marrow with variable dyspoiesis primarily involving the myeloid & megakaryocytic lineages, mild to moderate reticulin fibrosis, & mildly increased myeloblasts
Flow cytometric analysis:
↑ in CD34/CD117 positive hematopoietic progenitor cells (5-6%) with expression of HLA-DR, CD13, CD33 & aberrant CD56
Of uncertain significance
Special stains for AFB & fungal organisms were negative

25. Follow Up Con’t Treatment:
Solu-Medrol for hemophagocytic lymphohistiocytosis
Induction chemotherapy with MEC
Occasional fevers, but liver function tests normalized & has had continued improvement in weakness & fatigue
Bone marrow biopsies (10/29/15 & 11/13/15):
No increase in blasts
No features of hemophagocytosis

26. Interesting Features
It is unusual to see a case of AML associated with frank hemophagocytic lymphohistiocytosis
This phenomenon is different from that seen in AML with t(8;16)(p11.2;p13.3), KAT6A(MYST3)-CREBBP fusion, in which the blasts themselves demonstrate erythrophagocytosis1
In this case, the hemophagocytosis was an entirely different process

27. Interesting Features Con’t
Blasts versus lymphoma
Initially there was a cytologic diagnostic dilemma
Particularly in light of the presence of hemophagocytosis & only exceedingly rare apparent Auer rods
Flow cytometric findings confirmed blasts & excluded lymphoma

28. Interesting Features Con’t
Normal karyotype but FISH positive for RUNX1-RUNX1T1 fusion with a FISH signal pattern consistent with a balanced t(8;21)(q22;q22)
The expected balanced FISH signal pattern in the interphase nuclei strongly suggests this is not a cryptic translocation which indicates the normal chromosome result is distinctly unusual
In our practice we do not routinely perform FISH for abnormalities that are not known to be cytogenetically cryptic
In this case, it was only an afterthought to order FISH for t(8;21) after we discovered that the tumor cells were in fact blasts (& not lymphoma), were negative for the t(8;16), had single, thin Auer rods & expressed CD562,3
The lack of a t(8;21) AML clone to divide in a BM chromosome study is extremely unusual & suggests that the BM milieu was such that the blasts were inhibited from dividing

29. References Haferlach et al. Leukemia 2009;23:934-43.
Hurwitz et al. Blood 1992;80:
Swerdlow et al. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th edition.