Submitting Author: Gibson, Sarah Elizabeth, MD
Institution: University of Pittsburgh School of Medicine
Session: Therapy-related myeloid neoplasms

The patient is a 71-year-old male with a past medical history of Crohn’s disease receiving 6-mercaptopurine for a period of over 10 years. The patient was diagnosed with primary amyloidosis in 2010. Further testing showed a small serum IgA lambda monoclonal protein (0.21 g/dL), and a bone marrow biopsy showed unremarkable trilineage hematopoiesis and no evidence of involvement by a plasma cell neoplasm. The patient was completely asymptomatic and was followed for 14 months with no treatment. However, during this period the patient developed progressive pancytopenia. His 6-mercaptopurine was discontinued for approximately 1 month with no improvement in his peripheral blood counts. A bone marrow biopsy was then performed (see case).

Following this bone marrow evaluation, the patient was treated with 5-azacitidine. He received 7 cycles of 5-azacitidine over a 7 month period with almost complete normalization of his peripheral blood counts. However, after his 8th cycle, his hemoglobin and platelet count precipitously decreased over a 1 month period requiring red blood cell transfusions. A subsequent bone marrow biopsy was performed (see case).

The patient was then transferred to another hospital for treatment and was lost to follow-up.

1st bone marrow biopsy: right posterior iliac crest aspiration, biopsy, and peripheral blood smear

Fixation: formalin

Microscopic description:

Peripheral blood:

WBC 2.7x10^9/L (4.4 – 11.3)

Hemoglobin 9.9 g/dL (14.0 – 17.5)

MCV 85.3 fL (80.0 – 96.0)

RDW 24.6%

Platelets 50x10^9/L (150 – 450)

Neutrophils 45%

Lymphocytes 37%

Monocytes 18%

Nucleated red blood cells 3/100 WBC

The red blood cells demonstrate mild anisopoikilocytosis. Rare neutrophils appear hypogranular and rare pseudo-Pelger-Huet forms are present. Occasional giant and hypogranular platelets are seen.

Bone marrow:

The bone marrow is markedly hypercellular (90% cellular) with a myeloid/erythroid ratio of 0.5. Erythroid maturation is complete with megaloblastoid changes and dyserythropoietic forms with nuclear budding, binucleation and karyorrhexis. An iron stain shows rare ring sideroblasts (5 ring sideroblasts/100 erythroid precursors). Myeloid maturation is complete with approximately 4% blasts on the manual differential count. Occasional granulocytes appear hypogranular and some megaloblastoid and pseudo-Pelger-Huet forms are present. Megakaryocytes are increased in number and include many dysplastic hypolobated forms. Plasma cells comprise approximately 12% of cells in the bone marrow and are predominantly small and mature in appearance. A Congo Red stain performed on the biopsy is negative for amyloid deposition.

2nd bone marrow biopsy: left posterior iliac crest aspiration, biopsy and peripheral blood smear

Fixation: formalin

Microscopic description:

Peripheral blood:

WBC 8.1x109/L (4.4 – 11.3)

Hemoglobin 8.8 g/dL (14.0 – 17.5)

MCV 87.4 fL (80.0 – 96.0)

RDW 16.9%

Platelets 38x109/L (150 – 450)

Segmented neutrophils 6.5%

Bands 11%

Lymphocytes 22%

Monocytes 7%

Eosinophils 4%

Basophils 1.5%

Blasts 19%

Promyelocytes 13%

Myelocytes 15%

Metamyelocytes 1%

Nucleated red blood cells 2/100 WBC

The red blood cells demonstrate mild anisopoikilocytosis. Circulating blasts are present and are intermediate in size with a high nuclear:cytoplasmic ratio, fine chromatin and prominent nucleoli. Many blasts contain cytoplasmic granules. Dysplastic neutrophils with hypogranularity and/or pseudo-Pelger-Huet anomaly are also present.

Bone marrow:

The bone marrow appears hypercellular in the small amount of marrow present in the biopsy. Erythroid maturation is complete with megaloblastoid changes and occasional

dyserythropoietic forms. Myeloid maturation is left shifted with numerous blasts similar to those seen in the peripheral blood. There is dysgranulopoiesis with hypogranularity and pseudo-Pelger-Huet forms. Occasional dysplastic megakaryocytes are also present.

1st bone marrow biopsy:

Flow cytometry:

Flow cytometric immunophenotypic studies demonstrated approximately 6% myeloblasts that are CD45+(dim), CD34+, CD117+, CD13/CD33+, CD33+, and HLA-DR+. The blasts are negative for CD14, CD15, CD36, CD64, CD11b, CD16, T-lineage markers (including CD3, CD4, and CD7), and B-lineage markers.

Immunohistochemistry:

CD138 – approximately 10-15% plasma cells

Kappa – Rare scattered positive plasma cells

Lambda – Majority of plasma cells are positive

2nd bone marrow biopsy:

Flow cytometry:

Flow cytometric immunophenotypic studies demonstrated approximately 43% myeloblasts that are CD45+(dim), CD34+(small subset ~8% of total events), CD117+, CD13+, CD33+, CD15+, CD64+(CD34+ subset negative), myeloperoxidase+(CD34+ subset negative), CD4+(CD34+ subset mostly negative), CD7+(CD34+ subset mostly negative). The blasts are negative for HLA-DR, CD14, CD36, TdT, CD3 (surface and cytoplasmic), CD10, CD19, and CD20.

1st bone marrow biopsy:

45,XY,del(5)(q13q33),r(7)(p13q21),-18, del(20)(q11.2q13.3)[cp13]

FISH:

81.7% 5q31 deletion (EGR1/D5S23:D5S721)

5.4% monosomy 7, 61.4% 7q31 deletion (D7Z1/D7S486)

4.3% trisomy 8 (D8Z2)

82.8% 20q12 deletion (D20S10)

2nd bone marrow biopsy:

46,XY,del(20)(q11.2q13.3)[1]/44~45,XY,hsr(4)(q31),-5,+6,der(6)(pteràp21.3::p21.1à p10::p10àp21.1::p21.3àpter),del(7)(q22q36),der(7)add(7)(p15)add(7)(q22),+?r(7)(p13q21)x1~2,dup(11)(q23q25),-12,-16, der(18)t(14;18)(q24;q21),del(20)(q11.2q13.3),7~>90dmin[cp10]

None performed.

This case represents a therapy-related myeloid neoplasm arising in a patient receiving 6-mercaptopurine for Crohn’s disease. Even before the era of immunomodulatory therapy, an increased risk of developing myelodysplastic syndromes or acute myeloid leukemia was noted in patients with inflammatory bowel disease.1,2 Therapy-related myeloid neoplasms in patients with inflammatory bowel disease treated with thiopurines (azathioprine or 6-mercaptopurine) have been occasionally reported in the literature. Abnormalities of chromosomes 5 and 7, as seen in the current case, have been commonly reported in thiopurine-related myeloid neoplasms.3,4

Another interesting feature of this case is the phenotypic change of the blasts over the course of therapy with 5-azacitidine. In the initial bone marrow biopsy with fewer myeloblasts (6% blasts by flow cytometry), the prominent population was CD34+, CD117+, CD13/CD33+, and HLA-DR+. After 8 cycles of 5-azacitidine the CD34+ blast population was still present, but represented a minority of the myeloblasts (8% of total events by flow cytometry), with the prominent blast population lacking CD34 and HLA-DR expression, and expressing CD117, CD13/CD33, CD15, CD64, myeloperoxidase, CD4, and CD7. This change in phenotype was associated with the acquisition of additional clonal cytogenetic abnormalities.

References:

1. Harewood GC, Loftus EV, Tefferi A, et al. Concurrent inflammatory bowel disease and myelodysplastic syndromes. Inflamm Bowel Dis 1999;5:98-103.

2. Fabry TL, Sachar DB, Janowitz HD. Acute myelogenous leukemia in patients with ulcerative colitis. J Clin Gastroenterol 1980;2:225-7.

3. Heizer WD, Peterson JL. Acute myeloblastic leukemia following prolonged treatment of Crohn’s disease with 6-mercaptopurine. Dig Dis Sci 1998;43:1791-3.

4. Offman J, Opelz G, Doehler B, et al. Defective DNA mismatch repair in acute myeloid leukemia/myelodysplastic syndrome after organ transplantation. Blood 2004;104:822-28.

Therapy-related myeloid neoplasm associated with 6-mercaptopurine therapy.

Acute myeloid leukemia, possibly therapy-related, following 6-mercaptopurine therapy

Case 182