Submitting Author: Ramos, Jeanette Marie, MD
Institution: University of Arkansas for Medical Sciences
Additional authors:Marwan Yared
Session: AML with recurrent genetic abnormalities Part I

A 56-year-old female with past medical history of hypertension, diabetes mellitus, and depression presented to her primary care provider with large areas of bruising on her left upper extremity and back. Laboratory studies revealed a new severe pancytopenia: Hemoglobin 6.6 g/dL, white blood cell count 0.8, and platelet count 39,000 (K/uL). Other than a herpetic flare a month prior to presentation treated with valacyclovir that had clinically resolved, the patient had been feeling well. She had joined a diet program and had lost an intentional twenty-five pounds over six months. She denied night sweats, fever, joint pain, and headache. Physical exam revealed the previously described areas of ecchymosis but elicited no other abnormalities. Initial differential diagnosis included valacyclovir-induced bone marrow failure, herpetic involvement of the bone marrow, leukemia, or another bone marrow production defect.

Initial peripheral smear review demonstrated pancytopenia with circulating blasts, comprising 15-20% of the lymphocytes. The blasts were lobulated and granular, and flow cytometric studies were ordered to rule out acute promyelocytic leukemia. A bone marrow biopsy and aspirate of the right iliac crest was performed, and a 1.7 x 0.2 x 0.2 cm core biopsy was obtained. The biopsy was received in acid zinc formalin (AZF), decalcified, and processed overnight. Microscopic evaluation of the biopsy showed a hypercellular bone marrow for age (90% cellularity) with increased immature granulocytic forms and decreased erythropoiesis and megakaryocytes. The aspirate revealed a population of abnormal promyelocytes, many with bi-lobed morphology and prevalent Auer rods with scattered faggot cells, comprising 65% of the differential count.

Flow cytometry of the peripheral blood revealed that the “blast” population comprised 15-20% of analyzed events with moderate CD45 expression and high side-scatter. The population was positive for CD117, CD33, CD15 (subset), and cytoplasmic myeloperoxidase (bright) and was negative for HLA-DR, CD56, and CD2. A small subset was positive for CD34. Subsequent flow cytometric analysis of the bone marrow demonstrated an identical phenotype with the “blast” population comprising 70% of events.

Cytogenetic analysis demonstrated an abnormal female karyotype: 46,XX,der(7)t(7;8)(q22;q22.1) in twelve of twenty cells, which correlates with the abnormal FISH results.

Fluorescent in-situ hybridization (FISH) studies for -5/del(5q), -7, t(8;21), t(11q23), and t(15;17)(q22;q21) showed normal signal patterns, but del(7q) and +(8q22) signal patterns were detected in 78% and 81% of cells respectively. An additional FISH study for the RARA dual color break-apart probe was ordered to rule out variant translocations and was also negative. Polymerase chain reaction (PCR) studies for t(15;17) PML-RARA were sent and were reported as negative. Another sample was sent to a separate lab, and the bcr-3 transcript was detected.

The morphology and clinical scenario highly suggested acute promyelocytic leukemia, especially when the patient developed retinoic acid (differentiation) syndrome. However, the cytogenetic and initial molecular studies for t(15;17) as well as variant translocations involving the RARA gene were negative. It was not until the second laboratory PCR analysis identified the bcr-3 transcript that a definitive diagnosis could be made. The bcr-3 transcript is associated with a cryptic t(15;17) translocation. Also, the bcr-3 transcript is associated with frequent expression of CD34 and CD2. A subset of the patient’s cells did express CD34, but CD2 expression was not present.

Acute Promyelocytic Leukemia with cryptic t(15;17)(q22;q12); PML-RARA

Acute promyelocytic leukemia with cryptic t(15;17)(q22;q12); PML-RARA

Case 110