Submitting Author: Kim, Annette Sunhi, MD, PhD
Institution: Vanderbilt University Medical Center
Additional authors:Mary Ann Thompson Arildsen, David Hea, Aaron Shaver
Session: Therapy-related myeloid neoplasms

The patient is a 61 year old male with a prior diagnosis of chronic lymphocytic leukemia (CLL) diagnosed 6 years ago when he presented with a WBC of 27 K/uL and increasing lymphadenopathy. No FISH studies are available for his early disease presentation. He received some unspecified chemotherapy that year at an outside institution and a year later received fludarabine, cyclophosphamide, and rituximab (FCR) at Vanderbilt University Medical Center with achievement of a first complete remission. The patient relapsed two years later with the identification of deletion of ATM on chromosome 11q22.3 and bone marrow involvement. A normal karyotype was demonstrated at that time. The patient achieved a second complete remission after an additional 6 cycles of FCR with growth factor support. All bone marrow studies during his therapy and the subsequent CR2 were associated with a normal karyotype. His therapy was complicated by cytopenias as well as incidental findings of 2 meningiomas, now status post stereotactic radiosurgery.

However, 7 months after achievement of CR2, the patient again presented with fever and pancytopenia. A bone marrow biopsy was performed for presumed relapsed disease. However, there was no significant involvement by the patient’s known CLL, but instead a new karyotypic abnormality. The patient was monitored for 4 months without progression of disease. During this time he received only a single cycle of decitabine. He then underwent stem cell transplantation with nearly full engraftment in the most recent study.

The patient is currently doing well from a hematologic standpoint with no evidence of CLL or MDS by morphology, karyotype (46,XX[20]), FISH (negative for MLL rearrangment), and molecular (IGH gene rearrangement product previously identified not seen) in both post-PBSCT marrows.

Three bone marrow biopsies were performed during the 4 months prior to stem cell transplantation. These biopsies were all performed as iliac crest random biopsies, with fixation of the biopsies in B-Plus.

Biopsy 1 demonstrated a mildly hypercellular marrow (50-60% cellularity) with trilineage hematopoiesis and a left shift in maturation of myeloid and erythroid elements. There was only minimal atypia in the erythroid lineage with no significant dysplasia in the other lineages. No increase in lymphocytes, plasma cells, or blasts (1% by manual differential) was identified.

Cell Percentage (535 cell count)

Blast 4.1

Promyelocyte 13.5

Myelocytes and Metamyelocytes 32.3

Bands and Segs 1.3

Eos 4.1

Basos 0.4

Monos 0.7

Lymphs 8.6

Plasma cells 1.7

NRBCs 28.8

Biopsy 2, performed 1 month after biopsy 1, demonstrated a normocellular marrow (30-40% cellularity) with trilineage hematopoiesis. The myeloid and erythroid lineages were no longer left-shifted, and erythroid atypia was limited to binucleation and nuclear budding. Myeloid elements were mildly megaloblastoid. There was no increased in lymphocytes, plasma cells, or blasts (2% by manual differential).

Cell Percentage (562 cell count)

Blast 1.6

Promyelocyte 4.4

Myelocytes and Metamyelocytes 42.0

Bands and Segs 18.9

Eos 2.5

Basos 0

Monos 0.4

Lymphs 4.1

Plasma cells 0.4

NRBCs 25.8

Biopsy 3, performed 3 months after biopsy 1, was notable for increased cellularity (60-70% cellularity) with trilineage hematopoiesis and mild erythroid dysplasia (nuclear budding and irregular nuclear contours), and occasional neutrophils demonstrating hypogranulation and hypolobation. Blasts were not increased (2% by manual differential). There was no increase in lymphocytes or plasma cells.

Cell Percentage (593 cell count)

Blast 1.3

Promyelocyte 2.2

Myelocytes and Metamyelocytes 30.0

Bands and Segs 17.7

Eos 2.4

Basos 0.3

Monos 0.3

Lymphs 4.5

Plasma cells 0.8

NRBCs 41.3

Flow cytometry performed on biopsy 1 demonstrated polytypic B cells and a mix of T cell subsets with no significant blast population.

Flow cytometry performed on biopsy 2 demonstrated virtually no B cells and a mix of T cell subsets. Blasts (1.7% of total events) had the following immunophenotype: CD19(negative), CD33(moderate), CD34(negative), CD45(dim), CD117(moderate), and HLA-DR(moderate). There were no immunophenotypic aberrancies of the maturing myeloid cells. There was an increase in mature, immunophenotypically unremarkable monocytes (16% of total event), which may represent partial blood contamination.

Flow cytometry performed on biopsy 3 demonstrates a minute CD19+ kappa-restricted population of B cells (0.03% of total events) with normal T cell subsets and 0.5% blasts.

The karyotype and FISH findings for the three bone marrows were as follows:

Bone marrow 1: 46,XY,t(11;19)(q23;p13.1)[20];

Abnormal for a rearrangement of MLL in 93% of cells.

Bone marrow 2: 46,XY,t(11;19)(q23;p13.1)[20];

Abnormal for a rearrangement of MLL in 95% of cells.

Bone marrow 3: 46,XY,t(11;19)(q23;p13.1)[19]/ 46,XY[1];

Abnormal for a rearrangement of MLL in 82% of cells.

Careful examination of additional FISH studies of bone marrow 2 on a particle preparation revealed the MLL gene breakapart not only in immature cells, but in clearly mature neutrophils as well. The putative partner for the balanced translocation with MLL is the ELL gene.

Bone marrows 1 and 3 each demonstrated a small clonal population by immunoglobulin gene rearrangement studies which were identical to that obtained from a previous marrow involved by the patient’s CLL. Gene rearrangement studies were unsuccessful on bone marrow 2.

This case presents the unusual acquisition of an MLL gene rearrangement without development of an overt acute leukemia over at least a 4 month period of time. In addition, the bone marrow features during this time were very minimally dysplastic. Therapy-related myeloid neoplasms generally fall into one of two categories. Those cases which present after therapy with alkylating agents or ionizing radiation typically present later (5-10 years after therapy) and more commonly with therapy-related myelodysplastic syndrome than an overt therapy-related acute leukemia. This cases are characterized by the unbalanced loss of chromosomal material on chromosomes 5 and 7 (monosomies 5 and 7 or deletions of the long arms of 5 and 7).

By contrast, those cases which follow therapy with DNA topoisomerase II inhibitors tend to present with a shorter latency period of 1-5 years and are characterized by balanced translocations, often involving the MLL gene locus on chromosome 11q23, although other translocations have also been implicated within this subgroup. These patients tend to present in an overt acute leukemic phase rather than as a myelodysplastic syndrome.

The patient in this case had seen no topoisomerase II inhibitors, to the best of our knowledge, and certainly had received none within the past 5 years, although he had been exposed to alkylating agents as well as radiation as part of his radiosurgery for meningioma. In addition, he presented with minimally dysplastic marrows which remained stable for at least 4 months with only a single cycle of decitabine given prior to stem cell transplantation. At no time did he display any increase in blasts in the marrow. It is unclear how long the patient might have continued in this stable condition without evidence of an acute leukemia, had he not undergone transplantation. It is curious that the patient’s CLL should have demonstrated loss of the ATM locus at 11q22.3, and that his balanced translocation in his therapy-related myeloid neoplasm should have had a break involving the 11q23 MLL locus. This case displays many of the standard features of therapy-related myeloid neoplasms while highlighting several unusual features.

Therapy-related myelodysplastic syndrome with MLL translocation.

Additional immunostains performed by conference consensus group:

CD34: Not increased
CD61: Highlights dysplastic micromegakaryocytes

Therapy related myeloid neoplasm, with t(11;19)(q23;p13.1)

Case 130