Tanizawa RS, Azevedo Neto RS, Kumeda CA, Leal AM, Ferreira PB, Velloso ED balanced chromosomal alterations involving 11q23 rearrangements, t(8;21), t(15;17), t(8;16) or inv(16).(8,9) The high frequency of complex karyotypes in MN-t indicates a fast-emerging resistance to conventional treatments used in de novo leukemia cases.(10,11) Typically, the clinical course progresses with high mortality and morbidity rates. Allogeneic HSCT is the only therapeutic modality with the potential to cure patients with MN-t.(7,12) Cytogenetic aberrations which are present pre-transplantation are associated with low disease-free survival.(13) A study conducted by the European Group for Blood and Marrow Transplantation (EBMT) on patients with MN-t who underwent allogeneic HSCT between 1981 and 2006 found, using multivariate analysis, that the progress of the disease was more favorable in patients with normal karyotypes.(7) The development of secondary MDS/MN associated with treatment by immunosuppressants has been documented in AA. However, this subgroup also includes patients with autoimmune diseases and patients submitted to solid organ transplants.(2,14,15) Immunosuppressants such as cyclosporine A (CyA), anti-lymphocyte or anti-thymocyte globulin (ALG/ATG), cyclophosphamide (CTX), azathioprine and the use of granulocyte colony-stimulating factor (G-CSF) appear to be involved in the etiology of MN.(16) The cytogenetic abnormalities most frequently found in MDS/MN after AA involve chromosomes 6, 7 and 8.(17) In some cases these alterations may progress with transient cytogenetic abnormalities, such as chromosome 8 trisomy, which is responsive to immunosuppression treatment, and trisomy of chromosome 6. However, monosomy 7, the most frequent cytogenetic abnormality, occurs in patients with minimal clinical response, in patients who relapsed with severe pancytopenia(18) or in those who took G-CSF for a long time.(14) Some authors admit the possibility of a pre- existent clone with chromosome 7 monosomy being present at the diagnosis of AA.(18) Cytogenetic abnormalities involving chromosomes 5 and 7 were found in patients with rheumatic diseases that progressed to secondary MN after being treated with cumulative doses of alkylating agents for long periods.(15) Myeloid neoplasms are rare in patients who received solid organ grafts, such as in heart, liver and kidney transplantations. However, the occurrence of these neoplasms seems to be related to maintenance immunosuppression that is basically composed of prednisone, cyclosporine and azathioprine. Thus, abnormalities involving chromosome 7 have been described in patients who received solid organ transplants, particularly those who were treated with azathioprine, a potent immunosuppressant that leads to chromosome instability.(2) The aim of the present work was to study the clinical and cytogenetic data of patients who were exposed to antineoplastic and/or immunosuppressive drugs and those that progressed from aplastic anemia to secondary myeloid neoplasia. 426 Methods A retrospective study was carried out involving 42 patients with secondary MN diagnosed between September 1987 and December 2008 at the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. Conventional cytogenetics was performed using bone marrow samples and in one case using peripheral blood, with supplemented RPMI 1640 culture medium without any mitogenic agent incubated for 24 and 48 hours in a CO2 incubator at 37°C, followed by G-banding.(19) The fluorescence in situ hybridization (FISH) technique was used to investigate possible chromosome 7 monosomies in cases in which the karyotype showed no abnormalities or in which no metaphases could be obtained. The CEP 7® Chromosome Enumeration DNA FISH Probe (Vysis, Inc) was employed according to the manufacturer's recommendations. The cut- off point for the probe had previously been established in the laboratory following international guidelines.(20) For this purpose, an inverted β function statistical test was used (Microsoft Excel), after analyzing 200 interphase nuclei from five negative control samples. For each batch of probes, a normal control sample was tested in parallel. Cases presenting more than 10% of interphase nuclei with a single signal for the chromosome 7 centromere, analyzed by two independent observers (RSST and CAK), were considered positive for monosomy 7. The molecular cytogenetic analysis was performed in samples previously fixed in Carnoy solution (methanol/acetic acid). The karyotype and FISH results were described according to the international nomenclature (ISCN 2009).(21) The karyotypes were classified as normal or abnormal (chromosome 7 monosomy, complex karyotypes with 3 or more clonal alterations and other patterns with < 3 clonal alterations). Whenever possible, 20 metaphases were analyzed. To be considered a clone, the same structural alteration or the gain of the same chromosome in two metaphases or the loss of the same chromosome in three metaphases had to be observed.(21) Statistical analysis was performed using the Kaplan- Meier product limit estimator (survival curves), log rank test to compare groups and Fisher's exact test for associations between variables. In addition to the cytogenetic parameters, other clinical, hematological, bone marrow aspirate and histological factors were submitted to the binary logistic regression test to evaluate overall survival (OS). The data were analyzed using version 16.0 of the Statistical Package for the Social Sciences (SPSS) Computer program. Results Clinical characteristics of the patients A total of 42 patients were evaluated, of which 23 (54.8%) were male and the median age was 53.5 (range: 4-88) years. Their previous conditions included oncohematological Rev Bras Hematol Hemoter. 2011;33(6):425-31