Case 347

Submitting Author: Perkins, Sherrie Lynn, MD, PhD
Institution: University of Utah/ARUP Laboratories, Salt Lake City, UT
Additional authors:Todd Kelley MD, Mohamed Salama MD, Jerry Hussong MD
Session: AML with recurrent genetic mutations Part II

HISTORY

The patient is a 41 year old male who presented with a marked leukocytosis (143 K/uL), anemia, and thrombocytopenia.

DETAILS

The peripheral blood contained 95% blasts by differential count. Some of the blasts contained occasional cytoplasmic granules but no Auer rods were identified. The bone marrow aspirates were richly cellular and contained 97% blasts by differential count. No significant dysplasia was identified. The bone marrow core biopsy was hypercellular at 95%. The majority of the marrow elements consisted of immature mononuclear cells consistent with blasts.

IMMUNOHISTOCHEMISTRY AND FLOW CYTOMETRY

By flow cytometry immunophenotyping, the blasts expressed dim CD45, CD33, CD123, partial CD117, partial CD56 and myeloperoxidase but not CD34 or HLA-Dr. By cytochemical staining, the blast population was strongly positive for myeloperoxidase and focally and weakly positive for NSE (<20% of blasts positive). The blast population was negative for TdT by immunohistochemical staining.

CYTOGENETIC FINDINGS

Normal male karyotype (46, XY [7] ) in limited study. Negative for MLL rearrangement, t(15;17), inv(16) and t(8;21) by FISH.

MOLECULAR FINDINGS

NPM1 Mutation detected. No FLT3, CEBPA or Kit mutation detected.

INTERESTING FEATURES

Presentation of high peripheral blood white blood cell count with myeloid blast population negative for CD34 and HLA-Dr. Although the immunophenotype was suspicious for acute promyelocytic leukemia, the molecular and cytogenetic findings did not support that diagnosis.

PROPOSED DIAGNOSIS

Acute Myeloid Leukemia, NOS most consistent with AML Without Maturation (FAB-M1)

CONSENSUS DIAGNOSIS

Acute myeloid leukemia, NOS, with NPM1 mutation