Myelodysplastic syndrome (MDS) is characterized by trilineage morphological abnormalities and ineffective haemopoiesis, and is recognized as a preleukaemic disorder. The blast cells in leukaemia transformed after MDS usually display a myeloid phenotype. Although lymphoid progression has been reported previously (San Miguel et al, 1991; Kouides & Bennett, 1995; Escudier et al, 1996; Kohno et al, 1996; Pajor et al, 1998), there are no previously reported cases that transformed to acute lymphoblastic leukaemia (ALL) (L3). Here, we present the first report of a patient with MDS who transformed to Burkitt's ALL.
We describe a patient with myelodysplastic syndrome (MDS) that transformed to Burkitt's acute lymphoblastic leukaemia (ALL). The leukaemic blasts were negative for peroxidase staining, and expressed CD10, CD19, CD22, CD38, human leucocyte antigen (HLA)-DR and surface immunoglobulin (sIg) M, but neither sIgD nor sIgG were expressed. Chromosomal study during the ALL phase showed t(8;22)(q24;q11) in addition to the karyotypes determined during the MDS phase. Furthermore, overexpression of c-myc mRNA was confirmed in ALL blasts. These findings indicate that MDS transformed to Burkitt's ALL through multiple cytogenetic evolutions, the final event of which seems to be overexpression of the c-myc gene.
A 50-year-old Japanese man presented to our outpatient centre in September 1999 with 3·6 × 109/l white blood cells (WBC), 7·5 g/dl haemoglobin and 105 × 109/l platelets. He had a past history of laryngeal carcinoma treated with 66 Gy of local irradiation and two courses of chemotherapy using 800 mg of Cis-platinum and 10 g of 5-fluorouracil as total doses in July 1997. Physical examination showed neither lymphadenopathy nor hepatosplenomegaly. Bone marrow aspiration revealed a normocellular marrow containing 2·0% blasts. Morphological abnormalities were observed in all three cell lineages. Chromosomal abnormalities were detected in bone marrow cells, and most showed –Y and del(13)(q12;q14) (Table I). The patient had various cytogenetic abnormalities at first examination, including add(12)(p11), which is typical in MDS. The patient was diagnosed as having refractory anaemia (RA) and treated with Vitamin D3.
|Number of the cells||Karyotypes|
|At the first examination:|
|14/20||44, X, –Y, der(5)t(5;7)(q13; p11), −7, add(12)(p11), del(13)(q12;q14)|
|1/20||41, idem, −10, −14, −8, −20, +mar|
|1/20||44, X, –Y, der(5)t(5; 12)(q11; q13), −7, −12, del(13)(q12; q14) +mar|
|1/20||46, XY, t(3;11)(p25;q13)|
|At progression to leukaemia:|
|5/20||44, X, –Y, der(5)t(5; 7)(q13; p11), −7, add(12)(p11), del(13)(q12; q14)|
|3/20||44, idem, add(3)(q11)|
|1/20||45, idem, add(9)(q11), +12, -add(12), der(14)t(9;14)(q13; p11), ins(14;?)(p11;?), +mar1|
|8/20||47, X, –Y, t(8;22)(q24;q11), del(13)(q12;q14), +21, +mar2|
|3/20||46, X, –Y, t(8;22)(q24;q11), del(13)(q12;q14), −19, +21, +mar2|
|At post induction chemotherapy:|
|9/20||44, X, –Y, der(5)t(5;7)(q13;p11), −7, add(12)(p11), del(13)(q12;q14)|
|1/20||44, idem, add(11)(q23)|
|3/20||44, idem, add(6)(q15), add(11)(q23), −20, −22, +mar1, +mar2|
|4/20||44, idem, −2, −6, add(11)(q23), −19, +mar3, +mar4, +mar5|
|1/20||45, idem, add(9)(q11), +12, -add(12), der(14)t(9; 4)(q13;p11), ins(14;?)(p11;?), del(20)(q11q13.3)|
In January 2000, he was admitted to our hospital for investigation of femoral bone pain and developing leucocytosis of 196 × 109/l WBC with 66% blast cells. Bone marrow aspiration showed hypercellular marrow with 94·8% blasts which was negative for peroxidase staining. The leukaemic blasts varied in size with narrow basophilic cytoplasm, a few nucleoli and intracellular vacuoles. The cell surface markers, analysed using fluorocytometry, were as follows: CD5, 0·6%; CD7, 1·5%; CD10, 87·6%; CD13, 0·9%; CD19, 94·2%; CD20, 1·2%; CD22, 95·5%; CD33, 1·9%; CD34, 2·1%; CD38, 99·7%; human leucocyte antigen (HLA)-DR, 58·3%. Expression of surface immunoglobulin (sIg), which were also analysed using fluorocytometry, were as follows: sIgG, 0%; sIgM, 41%; sIgD, 1%. At this stage, cytogenetic analysis confirmed an additional chromosomal abnormality, t(8;22)(q24; q11) (Table I). Based on these data, the patient was diagnosed as ALL (L3). We treated him with vincristine, prednisolone, adriamycin, cyclophosphamide and l-asparaginase, and achieved morphological remission. Chromosomal abnormality of t(8;22)(q24;q11) had disappeared from bone marrow cells at morphological remission.
Materials and methods
Cytogenetic analysis Chromosomes were analysed using standard techniques and Giemsa Trypsin G bandings.
Northern blot analysis Total RNA was extracted using the guanidium isothiocyanate procedure from the leukaemic blasts, and was purified into poly A tail RNA with Oligotex™-dT30 (Takara Co., Tokyo, Japan). The denatured mRNA (5 µg) was electrophoresed in 1% agarose gel containing 2·2 mol/l formaldehyde, transferred to nylon membrane, and hybridized with a [32P]-labelled probe. The membranes were autoradiographed at −80°C. The nucleotide probe for human genomic c-myc and glyceraldehyde 3-phosphate dehydrogenase (G3PDH) were obtained from Takara Co., and Clonetech Laboratories (Palo Alto, CA, USA) respectively.
The karyotype of the bone marrow cells showed complicated abnormalities at diagnosis of MDS, ALL phase and after chemotherapy for ALL, which are summarized in Table I. The expression of c-myc mRNA in the leukaemic blasts was much stronger than that in human placenta or Raji cells, which is a human Burkitt's lymphoma cell line overexpressing c-myc (Hamlyn & Rabbitts, 1983) (Fig 1). The rearrangement of Ig heavy- and light-chain gene was detected in leukaemic cells at the original diagnosis of ALL (data not shown).
MDS is a preleukaemic abnormality involving a stem cell disorder that evolves to acute leukaemia in 15–70% of patients. Blast cells in leukaemia transformation after MDS are usually of myeloid lineage. Clonality studies indicate that the majority of MDS cases show monoclonality of the myeloid lineage (Van Kamp et al, 1992), and monoclonality of lymphocytes was detected in 7% of MDS patients only (Culligan et al, 1992; Van Kamp et al, 1992). Although over 20 cases of lymphoid transformation have been reported previously (San Miguel et al, 1991; Kouides & Bennett, 1995; Escudier et al, 1996; Kohno et al, 1996; Pajor et al, 1998), most displayed a myeloid–lymphoid hybrid or early B phenotypes, and CD10+ common ALL is rare. Furthermore, there were no reported cases of ALL(L3) transformation after MDS showing blast cells that originated from immature B cells. In our case, the blast cells displayed CD10, CD19, CD22, CD38 without any markers on other lineages, and clonal Ig heavy- and light-chain rearrangement. Moreover, expression of sIgM, but not sIgD or sIgG, was detected. These data proved that the origin of the leukaemic cells was immature B-cells. Although CD20 was not expressed on the blasts, we diagnosed this case as ALL(L3). The cytogenetic study demonstrated that the ALL and MDS clone shared –Y and del(13)(q12;q14) abnormalities, and t(8;22)(q24;q11) disappeared after induction chemotherapy (Table I). The chromosomal abnormality del(13)(q12;q14) is well documented in both MDS and ALL. Although we did not directly prove the clonal identity between MDS and ALL cells, it is hard to consider that del(13)(q12; q14) occurred by chance in the same patient within a period of only 4 months, leading to two independent haematological disorders. These findings strongly suggested clonal progression from MDS to ALL(L3). Furthermore, the patient had a history of laryngeal carcinoma treated with chemotherapy and radiotherapy, and a complex karyotype was seen, including the abnormality of chromosome 12p11, which is known in secondary MDS. These factors may be inducers of genetic changes leading to MDS and/or ALL(L3).
Constitutive overexpression of c-myc is deeply involved in tumourigenesis of Burkitt's lymphomas. As a reason for c-myc dysregulation, chromosomal translocation between c-myc on chromosome 8q24 and the IgH locus on chromosome 14q32, κ locus on chromosome 2p11 or λ locus on chromosome 22q11 are well known. Their juxtaposition to c-myc drives inappropriately high levels of c-myc mRNA and protein expression because Ig enhancer elements are specifically active in mature B cells (reviewed by Hecht & Aster, 2000). Rare translocations involving bvr-1 and pvt-1 loci, which are located 120–140 kbp and 260–280 kbp downstream of c-myc, respectively, have also been described in plasmacytoma and some Burkitt's lymphoma cell lines [summarized by Siwarski et al (1997) and Rack et al (1998)]. Although the mechanisms of c-myc overexpression in these cases have yet to be clarified, overexpression of c-myc has been proven (Shaughnessy et al, 1994). In our case, chromosomal abnormality of t(8;22)(q24;q22) and overexpression of c-myc mRNA was proven. These findings strongly suggested that, in this case, MDS transformed to Burkitt's ALL through overexpression of the c-myc gene. In this case, we could not detect rearrangement of c-myc in Southern blot analysis (data not shown), and rearrangement of pvt-1 or bvr-1 may have occurred.
Finally, to our knowledge, this is the first report of Burkitt's ALL transformation after MDS. This case suggests that clonal expansion leading to acute leukaemia from MDS takes place even at the stage of immature B cells on rare occasions.