[1543] CD56 Expression as a Reactive Phenomenon in Myeloblasts, Monocytes, and Granulocytes after Chemotherapy for Lymphoblastic Leukemia

Charles M Zaremba, Nitin J Karandikar, Franklin S Fuda, Sara A Monaghan, Jacqueline Emmons. University of Texas Southwestern Medical Center, Dallas, TX

Background: CD56 is normally expressed on NK cells and subsets of T lymphocytes. Aberrant expression can be seen on various hematolymphoid neoplasms including plasma cell neoplasms, acute myeloid leukemias, myelodysplastic syndromes, and myeloproliferative neoplasms as well as in reactive conditions, specifically on granulocytes and monocytes. Expression of CD56 on myeloblasts (MBs) is generally considered indicative of neoplasia. This study aimed to assess whether CD56 expression in MBs can be a reactive phenomenon, similar to granulocytes and monocytes.
Design: 48 follow-up bone marrow aspirates (BMAs) from patients with B or T lymphoblastic leukemia (LL) 29 to 90 days post induction chemotherapy were prospectively analyzed by four-color flow cytometry (FC). A combination of light scatter properties and antibodies for CD34, CD117, CD56, and CD45 were used to assess CD56 expression on MBs, granulocytes, and monocytes. 16 negative lymphoma staging BMAs served as controls. Clinical data, including chemotherapy received, use of growth factor therapy (GFT), and results of morphologic evaluation of the marrow, was collected from the medical record and pathology databases.
Results: Of the 48 LL follow-up BMAs, CD56 expression was detected in MBs in 7 cases (14.6%), granulocytes in 12 cases (25.0%), and monocytes in 31 cases (64.5%) using 10% as a positive threshold. Using a 20% cutoff, we detected CD56(+) MBs in 5 cases (10%), CD56(+) granulocytes in 5 cases (10.0%), and CD56(+) monocytes in 19 cases (39.5%). The CD56(+) MB populations showed a range of 14-96% cells positive, and they showed no additional immunophenotypic aberrancies. To date, no patients have subsequently developed myeloid neoplasms. Of the 7 patients with CD56(+) MBs, 3 had recently received GFT. There was no record of recent GFT in the remaining cases. In the lymphoma staging BMAs, CD56 expression was found only on monocytes in 2 cases (12.5%), but not on MBs or granulocytes.
Conclusions: By FC, we were able to detect CD56 expression on MBs 29 to 90 days after induction chemotherapy for LL. Our results demonstrate that similar to monocytes and granulocytes, CD56 expression can occasionally be detected in reactive/regenerative MBs and does not always equate with myeloid neoplasia. In at least 3 of the 7 cases where CD56(+) MBs were detected, the patient had recently received GFT, raising the possibility that GFT may contribute to aberrant CD56 expression on myeloid cells; however, additional studies are necessary to further investigate the possible relationship.
Category: Hematopathology

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 211, Wednesday Afternoon


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