Submitting Author: Juskevicius, Ridas, MD
Institution: Brody School of Medicine at East Carolina University
Additional authors:Jonathan D. Boyd
Session: AML with myelodysplasia-related changes

The patient was a female in her early 80s with history of hypertension, diabetes, TIA, mild dementia and coronary artery disease who presented to an outside hospital for arm pain. She was subsequently transferred to our institution for pancytopenia (Hgb 7.2mg/dL, Plt 65k/uL, Neutrophil 1.8k/uL) with schistocytes. She had recently been placed on Plavix and was suspected to have drug related TTP. Laboratory studies, however, revealed elevated fibrinogen (473mg/dL), elevated LDH of 2548 U/L (our lab normal range 122-240 U/L) with normal haptoglobin (206mg/dL) and creatinine kinase (60U/L). Additionally, occasional immature myeloid cells and nRBCs were seen on peripheral blood smear raising concern for a myelophthisic process and bone marrow examination was performed. No prior CBC or peripheral smear data or historic information indicating antecedent chronic cytopenias were available. After the diagnosis, the patient did not receive any cytotoxic chemotherapy due to significant comorbidity. The patient developed hypercalcemia and increasing mental status change, but remains alive with comfort care measures and management of hypercalcemia (~3 months after the diagnosis).

There was no bone marrow aspirate due to dry tap. Formalin-fixed, paraffin-embedded H&E stained marrow biopsy sections from the right superior posterior iliac spine demonstrated diffuse infiltrate of atypical mononuclear cells in a background of unusual loose myxoid-appearing granular stroma. The atypical cells had very irregular, occasionally polylobated nuclei and in many areas showed "nesting", "sinusoidal" or "single file" growth pattern somewhat mimicking solid malignancy, especially given unusually-appearing myxoid-like background. Only a small focal area of residual trilineage hematopoiesis with few non-dysplastic megakaryocytes was seen and this area was surrounded and encroached upon by this abnormal infiltrate of atypical cells. Reticulin stain revealed no significant fibrosis and mucicarmine stain was negative.

Wright-Giemsa stained touch preparations revealed predominant population of immature mononuclear cells that were extremely large and had very irregular, convoluted or folded nuclei, occasionally prominent nucleoli and relatively abundant basophilic vacuolated cytoplasm without granules or Auer rods. Some cells showed somewhat more mature chromatin and resembled monocytic lineage. Insufficient residual hematopoietic cells were seen on touch preparations for evaluation of underlying morphologic dysplasia. Cytochemical staining with myeloperoxidase (MPO) and butyrate esterase was performed with functional controls and demonstrated that the majority of the immature cells were positive for butyrate esterase and negative for MPO.

Flow cytometry performed on a disaggregated portion of the bone marrow core biopsy showed a predominant population of cells with intense CD45 staining and very high side and forward scatter, corresponding to immature atypical monocytic cells seen on the touch preparations. Most of these cells had abnormal monocytic immunophenotype with expression of CD11b, CD33, HLA-DR, CD38, CD64, CD13 and CD14. There was also variable expression of CD15 and CD16 and strong uniform aberrant expression of CD56. There was no expression of CD34, CD117 or any specific lymphoid markers.

Immunohistochemical stains for CD56, CD68, CD15, CD34, CD117, CD30, CD45, CD3, CD20 and AE1/3 demonstrated that the neoplastic cells were positive for CD45, CD56, partially positive for CD68 and negative for all other markers.

Cytogenetic analysis on a portion of disaggregated bone marrow biopsy has revealed an abnormal hypertetraploid clone in 17 of 20 cells analyzed:

98, XXXX, +8, +8, +8, +8, der(9) t(1;9)(q21;q22), +16, +20

None

This case represents acute myeloid leukemia (AML) with a novel, previously not described translocation in a background of complex hypertetraploid cytogenetics. The individual loci 1q21 and 9q22 are frequently involved in AML translocations with other partners (AF1q;MLL, MLLT3;MLL, ARNT;TEL, SYK;TEL, ZNF687;RUNX1) but this is the first documented case in which they occur together as partners. Also, the morphology is remarkable with a predominance of very large and atypical cells with irregular, convoluted variably immature nuclei in a background of myxoid-appearing stroma.

Based on morphologic features alone, the differential diagnosis of large cell lymphoma and possibly metastatic solid tumor was entertained initially. The relatively mature monocytic phenotype including strong coexpression of CD56 was also an interesting feature with very high side and forward scatter characteristics reflecting large cell size, relatively complex nuclei and probably cytoplasmic vacuolation. Although there was insufficient amount of more mature hematopoietic cells to assess for underlying dysplasia, we feel that this case represents AML with myelodysplasia-related changes, based on complex cytogenetics.

Several genes (AF1q, ARNT and ZNF687) at the 1q21 breakpoint have been implicated to have a role in AML. AF1q (1q21) is a gene of unknown function that has been shown to be a proliferative factor in breast cancer and expression levels of this protein have been shown to correlate with a poor prognosis in AML. ARNT (1q21) is a nuclear translocator that forms complexes with aryl hydrocarbon (dioxin) receptor and the hypoxia-inducible factor 1a and it is thought that disruption of that complex formation serves as a basis of leukemogenesis. ZNF687 (1q21) is a zinc finger transcription factor only known from a single report of AML resulting from RUNX1/ZNF687 fusion.

In this case the DNA binding portion of RUNX1 was missing from the fusion product but it was felt by the authors that the structure of the ZNF687 portion of the fusion product would allow it to bind DNA and function as a novel transcription factor.

Two genes (MLLT3/AF9 and SYK) at the 9q22 breakpoint have been implicated to have a role in AML. MLLT3/AF9 (9q22) is a transcription factor that has been shown to have anti-apoptotic effect when it complexes with AF4 (another MLL translocation partner). Additionally, in vitro, a therapeutic peptide has been able to induce apoptosis in AML cells by blocking the MLLT3 binding site of AF4. SYK (9q22) is a tyrosine kinase previously shown to play a role in B-cell differentiation and myelodysplasia. Also, RNAi and pharmacologic blockade of SYK has been shown to trigger maturation in numerous AML types and is being investigated as an AML therapeutic target.

Interestingly, AF1q and MLLT3 both form fusion proteins with the methyltransferase gene MLL which result in AML with monocytic features. Both ARNT and SYK can form a fusion product with the transcription factor TEL which has been seen in AML-M2 and RAEB, respectively. A protein product resulting from fusion of any of these genes could have played a leukemogenic role in our case presented here.

Acute myeloid leukemia with myelodysplasia-related changes

Acute myeloid leukemia with myelodysplasia-related changes (complex karyotype including hyperdiploidy)

Case 81