Incidence, characterization and prognostic signi®cance of chromosomal abnormalities in 640 patients with primary myelodysplastic syndromes F RANCESC S OLE  , 1 B LANCA E SPINET, 1 G UILLERMO F. S ANZ , 2 J OSE  C ERVERA, 2 MARõ ÂA J OSE  C ALASANZ , 3 E LISA L UN Ä O, 4 F ELIX P RIETO, 2 I SABEL G RANADA , 5 J ESU  S M a H ERNA  NDEZ , 6 J UAN C RUZ C IGUDOSA, 7 J OSE  L Uõ ÂS D IEZ , 8 E NCARNA B UREO, 9 MARõ ÂA L UISA MARQUE  S , 10 E VA A RRANZ , 11 R AFAEL Rõ Âos, 12 J OSE  A NGEL MARTõ ÂNEZ C LIMENT, 13 T ERESA VALLESPõ  , 14 L OURDES F LORENSA 1 AND S OLEDAD WOESSNER 1 `Grupo Cooperativo Espan Äol de Citogene Âtica Hematolo Âgica': 1 Hospital de l'Esperanc Ëa/Hospital del Mar/Hospital Central l'Alianc Ëa (Barcelona), 2 Hospital la Fe  (Valencia), 3 Hospital Universitario (Pamplona), 4 Hospital de Asturias (Oviedo), 5 Hospital Germans Trias i Pujol (Badalona), 6 Hospital Universitario de Salamanca (Salamanca), 7 Universidad de La Laguna (Tenerife), 8 Clõ Ânica Puerta de Hierro (Madrid), 9 Hospital Universitario Marques de Valdecilla (Santander), 10 Hospital 12 de Octubre (Madrid), 11 Fundacio Ân Jimenez Diaz (Madrid), 12 Hospital Comarcal `Valle de los Pedroches' (Cordoba), 13 Hospital Clõ Ânico Universitario (Valencia), 14 Hospital Vall d'Hebro Ân (Barcelona) Received 1 August 1999; accepted for publication 4 October 1999 Summary. Recently, a consensus International Prognostic Scoring System (IPSS) for predicting outcome and planning therapy in the myelodysplastic syndromes (MDS) has been developed. However, the intermediate-risk cytogenetic sub- group de®ned by the IPSS includes a miscellaneous number of different single abnormalities for which real prognosis at present is uncertain. The main aims of this study were to evaluate in an independent series the prognostic value of the IPSS and to identify chromosomal abnormalities with a pre- viously unrecognized good or poor prognosis in 640 patients. In univariate analyses, cases with single 1q abnormalities experienced poor survival, whereas those with trisomy 8 had a higher risk of acute leukaemic transformation than the remaining patients (P  0?004 and P  0?009 respectively). Patients with single del(12p) had a similar survival to patients with a normal karyotype and showed some trend for a better survival than other cases belonging to the IPSS intermediate- risk cytogenetic subgroup (P  0?045). Multivariate analyses demonstrated that IPSS cytogenetic prognostic subgroup, proportion of bone marrow blasts and haemoglobin level were the main prognostic factors for survival, and the ®rst two characteristics and platelet count were the best predictors of acute leukaemic transformation risk. A large international co-operative study should be carried out to clarify these ®ndings. Keywords: myelodysplastic syndromes, karyotype, cytogen- etics, prognosis, chromosomes. The myelodysplastic syndromes (MDS) constitute a hetero- geneous group of haematological disorders characterized by peripheral blood cytopenia(s) in the presence of hypercellular bone marrow with features of ineffective haematopoiesis. MDS have been associated with a high risk of progression to acute myeloid leukaemia (AML) and an overall short survival, death being generally due to the consequences of cytopenias or to progression to AML (Bennett et al, 1985). MDS are classi®ed by the French/American/British (FAB) group, based on the percentage of bone marrow and peripheral blood blasts, the percentage of bone marrow ringed sideroblasts and the level of circulating monocytes, into ®ve subtypes: refractory anaemia (RA); refractory anaemia with ringed sideroblasts (RARS); refractory anaemia with excess of blasts (RAEB); refractory anaemia with excess of blasts in transformation (RAEB-t); and chronic myelo- monocytic leukaemia (CMML). Although MDS are not associated with any speci®c chromosomal abnormalities, a high incidence of different British Journal of Haematology , 2000, 108, 346±356 346 q 2000 Blackwell Science Ltd Correspondence: Dr Francesc Sole Â, Laboratori de Citologia Hemato- lo Ágica, Laboratori de Refere Áncia de Catalunya, Unitat d'Hematologia 1973, Hospital del Mar, Passeig Marõ Âtim 25±29, 08003 Barcelona, Spain. e-mail: E0037@imas.imim.es.