Case Report: Blastic Natural Killer (NK) Cell Leukemia (Agranular CD4+CD56+ Leukemia) Kai Zhang, Jeffrey W. Prichard, and Robert E. Brown Division of Laboratory Medicine, Geisinger Medical Center, Danville, Pennsylvania Abstract. Blastic NK cell lymphoma is a rare hematolymphoid neoplasm. his report illustrates an unusual presentation of this entity, namely as a primary leukemia, but without skin lesions. Keywords: NK leukemia, plasmacytoid monocytes, CD4/CD56 Introduction Many types of leukemia and lymphoma are thought to originate from natural killer (NK) lineage cells, either from a precursor NK cell or mature NK cell [1]. he blastic NK cell lymphoma is considered as a hematolymphoid neoplasm and proposed to be derived from precursor NK cell. It is believed that it overlaps with, or may be identical to, the entity called primary cutaneous CD4+CD56+ hemato- lymphoid neoplasm [2-6]. his entity also has been termed “agranular CD4+CD56+ hematodermic neoplasm” [3]. Interestingly, recent studies suggest that this malignancy might possibly originate from plasmacytoid monocyte/interferon-producing cells (PM/IPCs) rather than precursor NK cells [3-6]. Case Report he subject of this report is an 85-yr-old white male who presented to the outpatient clinic with chronic fatigue and was found to have leukocytosis, anemia, and thrombocytopenia. Hematologic parameters included: white blood count (WBC), 88,000/µl with 90% blast-like cells; hemoglobin (Hb), 10.2 g/dl with mean corpuscular volume (MCV), 89 l; platelet count, 90,000/µl. Physical examination showed slight pallor and mild splenomegaly. here was no jaundice, nor skin lesions, nor palpable lymphadenopathy, nor hepatomegaly. Flow cyto- metric studies were performed on whole blood. Based on the low cytometric data, morphologic features of the leukemic cells, and results of T- and B-gene rearrangement (Figs. 1-3) a diagnosis of “blastic NK-cell leukemia” was made. Chromosomal analysis was performed on the bone marrow specimen at Genzyme Genetics (Fairfax, VA) and reported as follows: “an abnormal clone of the cells was identiied and the cells showed multiple numerical and structural abnormalities in 9 cells and the abnormal results were: 42-45, XY, del(5)(q11.2q33), add (12)(p11.2),-13, add(14)(q32),- 15,+mar[cp9]/46,XY{11}.” he patient declined to have chemotherapy. Two months later, the patient returned with worsening anemia and thrombocytopenia, blood Hb, 6.2g/dl, RBC, 1.99 x 10 6 /µl, MCV, 106.5 l, platelets, 21,000/µl, and WBC of 100,000/µl. Physical examination was essentially unchanged. No skin nodules or plaques were present. Bone marrow biopsy revealed sheets of leukemic cells replacing marrow. Repeat low cytometry of the marrow aspirate specimen showed leukemic cells with immunophenotypic features identical to the leukemic cells from the blood. Address correspondence to Kai Zhang, M.D., Division of Laboratory Medicine, Geisinger Medical Center, Danville, PA 17822-0131, USA; tel 570 214 9781; fax 570 271 6105; e-mail kzhang1@geisinger.edu. 0091-7370/06/0100-0212. $1.00, © 2006 by the Association of Clinical Scientists, Inc. Available online at www.annclinlabsci.org Annals of Clinical & Laboratory Science, vol 36, no. 2, 2006 212