Biclonal Chromosome Evolution of Chronic Myelomonocytic Leukemia in a Child Liliane Massaad, Marguerite Prieur, Claude Leonard, and Bernard Dutrillaux ABSTRACT: A monosomy 7 was first detected in a 6-month-old boy with a chronic myelomonocytic leukemia. After etoposide treatment, relapse occurred after 29 months, with transformation of the disease into an acute myeloblastic leukemia. After bone marrow transplanta- tions, two abnormal clones were found in marrow cells: 45,XY,-7,del(12)(pl lp12)(66%), and 45,XY,-7,t(3;12)(q26;p12)(33%). Several karyotypic studies performed until the terminal phase exhibited the persistence of these two clones in the same proportion, although both independently acquired additional and often similar anomalies. The clone with t(3;12) acquired der(7),der(11),der(17),der(8),der(lO),-5,-20, and the clone with del(12p), del(5q),der(4),der(8),der(10),der(17),-5,-20. The anomalies in 12p12 appear to represent an important although secondary event of the neoplastic process. The other anomalies may corre- spond to either those of a secondary acute nanlymphocytic leukemia, since they occurred after treatment by etoposide and alkylating agents, or to the natural evolution of myelomonocytic leukemia. INTRODUCTION Chronic myelomonocytic leukemia (CMMoL) and/or myelodysplastic syndromes (MDS) of childhood are principally characterized by monosomy 7 [1, 2]. Although this anomaly has been known for some time, little is known about secondary chro- mosomal changes associated with -7. Recently, a rearrangement involving chromo- some 11 was described in two children [3]. We report a case of CMMoL in a child in whom monosomy 7 was first detected. After bone marrow transplantation, further rearrangements occurred and two independent clones were observed until the termi- nal phase of the disease. This unusual chromosome evolution is described. CASE REPORT The diagnosis of a hematological disorder was first suspected in a 6-month-old boy. Fever, pallor, and hypotrophy were associated with hepatosplenomegaly, multiple enlarged lymph nodes, and hematodermy. Blood and bone marrow cell counts were characteristic of a chronic myelomonocytic leukemia (Table 1). A treatment with etoposide at age 9, 10, and 11 months stabilized the disease, and no signs of transfor- mation were noticed until age 29 months. At this age, transformation of the disease From the BiologySection (L. M., M. P., B. D.), Institut Curie and Laboratoired'HistologieEmbryologie Cytog6n~tique(C. L.), C.H. BicStre, BicStre,France. Address reprint requests to: Dr. Marguerite Prieur, Institut Curie, Section de Biologie, URA 620, C.N.R.S. 26, rue d'Ulm, 75231 Paris, Cedex 05, France. Received March 29, 1989; accepted June 30, 1989. 131 © 1990 Elsevier Science PublishingCo., Inc. Cancer Genet Cytogenet44:131-137 (1990) 655 Avenueof the Americas,New York, NY 10010 0165-4608/90/$03.50