[Triple Philadelphia chromosome during blastic crisis of a chronic myelocytic leukemia].

The blastic phase of a Ph1-positive chronic myeloid leukemia (CML) is often characterized by hyperdiploidy and sometimes by the presence of a double Ph1, suggesting a pattern of clonal evoluation. In the case reported here, the caryotype at the time of diagnosis in 1970 was 46, XY, Ph1. In 1975, after a blastic evolution followed by a drug-induced hematologic remission, cytogenetic studies revealed a chromosomal mosaic: 47, XY, 2 Ph1 and 51, XY, 3 Ph1, 3 C, the clone with 3 Ph1 representing approximately 20% of the mitotic cells. Furthermore, with the Giemsa banding technique, it was possible to identify the 3 supplementary C chromosomes of the 51 chromosomes clone, as being an 8, a 9 and 9 q + respectively. This observation illustrates the succession of chromosomal anomalies occurring during the evolution of CML with, in this case, the unusual appearance of a clone with 3 Ph1.