Submitting Author: Yu, Hongbo, MD, PhD
Institution: Department of Pathology, University of Massachusetts Medical School
Additional authors:Wei Xing, Jan Cerny, Bruce A. Woda
Session: AML with recurrent genetic mutations Part II

A 57-year-old woman with history of melanoma and hypertension visited emergency room with upper abdominal pain and discomfort in February 2010. CBC showed anemia, thrombocytopenia, mild leukocytosis with 33% blasts. Bone marrow biopsy and aspirate smears were performed and the patient was diagnosed with acute myeloid leukemia. During February to May, she received induction and consolidation cytarabine followed by cytarabine and etoposide mobilization. She was in remission and had autologous peripheral blood progenitor cell collection on 5/14/10.

However, by the end of May, she relapsed with 80-90% blasts in bone marrow. She was then treated with high-dose cyclophosphamide and etoposide followed by sorafenib.

Subsequently in early August, she underwent a matched sibling allogeneic stem cell transplantation following preoperative regimen consisting of thiotepa, fludarabine, melphalan chemotherapy, and had post-transplant cyclophosphamide. Her post-transplant bone marrow biopsy did not show any evidence of acute leukemia.

She was in remission until the first week of December 2010, when her clinical status began to gradually decline and frequent transfusions were necessary. She was hospitalized on 1/17/11 initially for epistaxis and thrombocytopenia. Bone marrow biopsy on 1/19/11 showed marked hypocellular marrow (5%) with hemophagocytosis. Her hospital stay was complicated by CMV viremia, neutropenia, septic shock, and multiple organ failure. She expired on 2/7/11.

Site: Posterior iliac crest

Method of fixation: Formalin

Gross: Bone marrow biopsy cores

Microscopic pathology: Bone marrow biopsy from 2/12/10 showed hypercellular (90-95%) marrow with numerous myeloblasts occupying 80% of the total cellularity. Rare erythroid elements, maturing myeloid elements and megakaryocytes were present. Bone marrow aspirate smears showed 83% blasts, which were small to intermediate in size, with round nuclei, dispersed chromatin, distinct nucleoli, and small amount of cytoplasm. No Auer rods were identified. Rare maturing myeloid elements, erythroid elements, and megakaryocytes were seen.

Bone marrow biopsy from 5/27/10 showed bone marrow was replaced by sheets of myeloblasts comprising 80-90% of the total cellularity. Bone marrow aspirate smears showed numerous blasts with similar morphologic features to the original leukemic blasts from 2/12/10.

Flow cytometry analysis from the bone marrow sample on 2/12/10 showed a population of myleoblasts with the following immunophenotype: CD34+ (subset), CD117+, CD13+, CD33+, HLA-DR+, CD7+ (dim), CD25+, MPO+, CD19-, CD3-, TdT-. This population consists of 64% of total nucleated cells. Approximately 23% of the myeloblasts were positive for CD25.

Flow cytometry analysis from the bone marrow sample on 5/27/10 showed a population of myleoblasts with the following immunophenotype: CD34+ (subset), CD117+, CD13+, CD33+, HLA-DR+, CD7+ (dim), CD25+, MPO+, CD19-, CD3-. This population consists of 46% of total nucleated cells. Approximately 60% of the myeloblasts were positive for CD25.

2/12/10

KARYOTYPE: 46,XX[20]

5/27/10

KARYOTYPE: 46,XX[20].nuc ish(MLLx2)[500]

Molecular analysis from the bone marrow sample on 2/12/10 detected a FLT3 internal tandem duplication (ITD) and an NPM1C mutation.

Molecular analysis from the bone marrow sample on 5/27/10 detected a FLT3 internal tandem duplication (ITD) and an NPM1C mutation.

CD25 (also known as interleukin 2 receptor receptor alpha, IL2 RA) expression is associated with a leukaemic stem cells (LSC) biology and chemotherapy resistance. High (>10%) at diagnosis in young (<60 years) acute myeloid leukaemia (AML) patient in retrospective analysis correlated with a significantly shorter overall survival (OS, P=0.0005) and replase. CD25 expression was also associated FLT3-internal tandem duplication (ITD) mutation and double positive patients had the poorest OS and RFS (P=0.01 and P=0.003, respectively).

The submitted case is a representative example of these patients. We examined the impact of CD25 expression among 45 patients with newly-diagnosed AML treated at out institution between February and May 2011. CD25 was detected in 14 patients at diagnosis. 57% patients with CD25+ AML had FLT3-ITD. Compared with CD25- AML, expression of CD25 at diagnosis was a strong predictor of treatment failure (induction failure and relapse); CD25+ patients displayed an increase in the percentage of CD25+ blasts at first treatment failure (induction failure or first relapse). The estimated 6-month cumulative incidence of relapse (CIR) was significantly worse in CD25+ patients compared to CD25- patients. Many CD25+ patient also FLT3-ITD mutation, which, in preclinical models, confers sensitivity to cytarabine, but resistance to anthracyclines. Thus, patients with FLT-3-ITD positive AML may not benefit from escalated anthracycline, but rather high dose cytarabine (HiDAC). We considered CD25+ patients for consolidation with allogeneic or autologous stem cell transplant (SCT) early in their disease course and observed that SCT appeared to abrogate the negative impact of CD25 expression on OS.

Acute myeloid leukemia with CD25 expression and FLT3 mutation

Acute myeloid leukemia with FLT3 ITD mutation [partially CD25 positive]

Case 52