1. Persistent plasmacytoid dendritic cell proliferation in the bone marrow
Submitted by Hebeda and MacKenzie
EAHP 2016 Bone Marrow Workshop EAHP16-BMWS-303

2. Clinical history July 2013: suspected Lyme disease, antibiotics.
August 2013: febrile illness with neutropenia, leukocytes 1,1 x10*9/l granulocytes 0,34x10*9/l , trombocytes 87x10*9/l ,
Hb 8.1 mmol/l. No etiology established.
October 2013: persistent neutropenia, tiredness, artralgia, intermittent fever and muscle ache. Splenomegaly (14 cm). No skin lesions. Infectious causes excluded.
PETscan shows multiple active lymph nodes throughout the body, polyartritis and an enlarged spleen.
BM biopsy, BM cytology, immunoflowcytometry, cytogenetics
Karyotyping: 46,XY[20]
Interfase FISH: no MLL (11q23) or ETV6 (12p13) rearrangement, 2 signals for ETV6 (12p13), EGR1 (5q31), LSI D5S23-
D5S721(5p15.2), RB1 (13q14), TP53 (17p13.1) [200]

3. Biopsy T

4. 2014 BM
CD123
CD123
CD123
TCL-1

5. Follow up October 2013: plasmacytoid dendritic cell neoplasia.
No response to antibiotic treatment for Lyme disease. Patient refuses chemotherapy and/or bone marrow transplant.
Supportive treatment (antibiotics if required)
Last follow-up BM biopsy May 2014: stable number of PDC’s.
December 2015: persistent neutropenia (leukocytes 1,3 x10*9/l, granulocytes 0,52x10*9/l).
Persistent 5-10% PDC's in BM smears and flowcytometry.
Stable clinical disease without treatment.

6. Hb
mm/L T
10*9/L

7. Interesting features the alignment of the PDC's along sinuses
the very indolent nature
need to establish a "normal" range of quantity, morphology and distribution of the PDC's
BDCA-2

8. PDC’s in staging and MDS BMB
Method:
* Histology BMB: 18 NHLstaging, 20 MDS
- anti-BDCA-2, specific for PDC’s.
- average number of positive cells per high power field (HPF) , distribution (scattered or clustered).
* flowcytometric immunofenotyping BM aspirate: 19 NHLstaging BMB, 41 MDS
- CD123 and HLA-DR
Results: The number of cases with aggregates > 6 PDC’s was equal, but the aggregates in MDS were in general much larger
>15 PDC’s in 7/7 cases with MDS, and in 3/7 normal BM.
Average number of PDC’s / HPF:
Staging: 4.6, range
MDS: 9.1, range
IFT % PDC’s:
Staging: range %
MDS: 0.03%-4.97%
In non-neoplastic BM the distribution of PDC’s shows a much more homogeneous pattern than in MDS. The latter shows extremes to both ends in number and aggregation of PDC’s.

9. BDCA-2