Case 411

Submitting Author: Gonzalez-Berjon, Jose M, MD
Institution: University of Texas MD Anderson Cancer Center
Additional authors:Tariq Muzzafar, MD
Session: Erythroleukemia and megakaryoblastic AML and mimics

HISTORY

Patient is a 50 year old male with no significant past medical history presented with two week history of fatigue, weakness, nose bleeding, weight loss, fevers and sweats. He went to the emergency room and was admitted directly to the intensive care unit in view or his clinical state. He was treated with idarubicin and ara-C 3+7 but had persistent disease. He was subsequently given high-dose ara-C and Mylotarg (x1) with refractory disease and liver toxicity. He presented to UTMDACC for treatment options 5 months later. CBC: WBC 4.0, Hgb 9.1, MCV 90, Platelet 3, Neutrophils 28%, Lymphs 63%, Monos 2%, Eos 1%, Bands 1%, Other unclassified cells = 5%

DETAILS

Bone marrow core biopsy (Formalin fixed after decalcification): 90% cellularity, sheets of immature cells replacing 90% of total cellularity; normal hematopoietic cells decreased profoundly Bone marrow aspirate smears: 93% blasts; blasts are predominantly large, with moderately dispersed chromatin, multiple distinct to prominent nucleoli, abundant, basophilic, agranular cytoplasm and pronounced pseudopod formation

Myeloperoxidase: Blasts are negative
Butyrate esterase: Blasts are negative

IMMUNOHISTOCHEMISTRY AND FLOW CYTOMETRY

Blasts are positive for CD13, CD34, CD36, CD41, CD61

CYTOGENETIC FINDINGS

Karyotype: 46,XY,del(9)(q22)[17] ;46,XY,del(9)(q22)[cp2] 46,XY[1]

MOLECULAR FINDINGS

NEGATIVE for PML-RARA short or long form fusion transcript, AML1-ETO fusion transcript, CBFb-MYH11 fusion transcript, mutations in FLT3 (internal tandem duplication or codon 835/836), K-ras and N-ras oncogenes (codons 12, 13 and 61)

INTERESTING FEATURES

Acute megakaryoblastic leukemia is a rare disease entity. We performed a study that demonstrated that only a small minority (10%) of cases with morphologic / immunophenotypic features of megakaryocytic differentiation can be classified as megakaryoblastic leukemia using WHO classification. Most cases of megakaryoblastic leukemia currently fit diagnostic criteria for acute myeloid leukemia with myelodysplasia-related changes. In our series, 12 (24%) cases evolved from a pre-existing myeloproliferative neoplasm, a finding not commonly emphasized. Megakaryoblastic differentiation occurs in a spectrum of hematologic neoplasms, with complex karyotype being a common feature. However; survival is poor in all instances. In this case, there was no antecedent history and presentation was acute, thus ruling out progression from underlying myeloid neoplasm.

PROPOSED DIAGNOSIS

Acute megakaryoblastic leukemia

CONSENSUS DIAGNOSIS

Acute megakaryoblastic leukemia