Kathryn D. Matney, MD, Lynne Meltesen, Karen Swisshelm, PhD, Zenggang Pan, MD, PhD

1. University of Colorado Denver | Anschutz Medical Campus A Novel Case of Clonal Myeloproliferative Disorder with Prominent Histiocytic Differentiation Kathryn D. Matney, MD, Lynne Meltesen, Karen Swisshelm, PhD, Zenggang Pan, MD, PhD Department of Pathology University of Colorado Denver/Anschutz Medical Campus Aurora, CO, USA

2. Clinical History • A 68-year-old female presented with a one-month history of fatigue, low-grade fever and dry cough. She was found to have splenomegaly, severe anemia (HGB 7.9g), mild leukocytosis (WBC 13.6K), and marked thrombocytopenia (PLT 5K). A bone marrow biopsy was performed; • The patient had persistent acidosis, anemia and thrombocytopenia despite multiple blood transfusions as well as steroid and intravenous immunoglobulin treatment; • A week later the patient rapidly developed respiratory distress requiring intubation and mechanical ventilation. She also developed a disseminated intravascular coagulation constellation, including an elevated prothrombin time (29.3 seconds), low fibrinogen (125 mg/dL), elevated D-dimer (7.18 μg/mL), and elevated lactate dehydrogenase (1,231 U/L); • She subsequently developed a fulminant sepsis-like picture with fever, hypotension, tachycardia, and leukocytosis. Clinical image studies revealed multifocal acute infarcts in the brain, gastrointestinal tract, spleen, liver and kidneys. The patient eventually passed away. This case was partially published on Ann ClinPathol 2014; 2(5):1034

3. Peripheral Blood Findings • Marked normochromic and normocytic anemia with frequent schistocytes; • Marked thrombocytopenia; • No atypical lymphocytes, dysplastic granulocytes or circulating blasts.

4. Bone Marrow Aspirate Smear • The bone marrow aspirate smears show abundant histiocytes with round, indented or crescentic nuclei and moderately condensed chromatin. The cytoplasm is abundant and pale-blue staining with frequent vacuoles and rare hemophagocytic activities; • The granulocytes, erythroid precursors and megakaryocytes show a complete maturational spectrum with no overt dysplasia; • No increase in blasts, lymphoma, metastatic tumor or obvious infectious process noted.

5. Bone marrow aspirate smear. Wright-Giemsa. 200×

6. Bone marrow aspirate smear. Wright-Giemsa. 1000×

7. Bone marrow aspirate smear. Wright-Giemsa. 1000×

8. Bone marrow aspirate smear. Wright-Giemsa. 1000×

9. Bone marrow aspirate smear. Wright-Giemsa. 1000×

10. Bone marrow aspirate smear. Wright-Giemsa. 1000×

11. Bone Marrow Core Biopsy • The bone marrow core biopsy shows a hypercellular marrow (80% cellularity) with patchy infiltration by histiocytes (~70% of marrow cellularity); • The remaining marrow tissue reveals normocellular marrow and active trilineage hematopoiesis with no overt dysplasia; • No increase in blasts, lymphoma, metastatic tumor or obvious infectious process noted.

12. Area with no histiocytic infiltration Area with patchy histiocytic infiltration Bone marrow core biopsy. HE. 40×

13. Patchy histiocytic infiltration. HE. 200×

14. Patchy histiocytic infiltration. HE. 400×

15. Patchy histiocytic infiltration. HE. 600×

16. Residual marrow with no histiocytic infiltration. HE. 200×

17. PAS-D CD1a CD68 S100

18. Summary of Immunohistochemical Stains and Special Studies • Histiocytes positive for CD68 but negative for CD1a and S100; • No abnormal lymphoid or blastic populations noted by CD3, CD20, CD30 and CD34 staining; • Cytokeratin stain negative; • No infectious microorganisms or abnormal intracytoplasmic deposits identified with AFB, GMS and PAS-D special stains.

19. Conventional Cytogenetic Studies • Karyotype: 46,XX,add(5)(q31),der(17;21)(q10;q10),der(20)t(5;20) (q31;q11.2)[11]/46, idem,+21,iso(21)(q10)[7]/46,XX[2] • Interpretation: • Multiple structural chromosomal abnormalities in 18 of 20 cells; • Eleven cells with one or more of the following: unknown additional material on the long arm of chromosome 5; an unbalanced translocation between chromosomes 5 and 20 resulting in a deletion in the long arm of chromosome 20; and an unbalanced translocation between the long arms of chromosomes 17 and 21 yielding a deletion of 17p; • Seven cells had an isochromosome 21q, in addition to the above mentioned abnormalities.

20. FISH Studies • Positive for 20q deletion in 84.5% of marrow cells; • No genetic alterations on chromosomes 5, 7, 8, or 13; • Since it was not clear which population of marrow cells exhibited 20q deletion, we performed additional FISH assays using the 20q probe on the Wright-Giemsa stained bone marrow aspirate smears to map the 20q deletion to specific marrow cell types. Multiple images were taken on the Wright-Giemsa stained marrow aspirate smears to match the cells on the same slides after FISH probe hybridization.

21. Additional FISH studies detected 20q deletion in all of the histiocytes (23 of 23 cells counted) and granulocytes (21 of 21 cells counted), whereas none of the 26 erythroid cells counted were positive for this deletion.

22. Proposed Diagnosis Clonal Myeloproliferative Disorder with Prominent Histiocytic Differentiation

23. Interesting Features • A myeloproliferative disorder show marked histiocytic differentiation; the histiocytes are mature-looking despite very mild atypia; • The histiocytes and the granulocytes appear to be clonally related; both of them harbor the same genetic alteration of 20q deletion; • The histiocytes display a patchy infiltrative pattern with focal residual normocellular marrow tissue left; • The granulocytes are also neoplastic although no overt dysplasia is noted.