Rings and double minutes in a case with blastic phase of chronic myelocytic leukemia.

The patient studied was a 33-year-old female in the blastic phase of chronic myelocytic leukemia resistant to busulfan. The results of cytogenetic studies of bone marrow cells were as follows: The abnormal chromosomes were double Ph1, +19, +6, +B, ring D, double ring D, double minutes (DM) of various sizes, etc. The mean number of DM per cell was increased in 4-day culture compared with that in 1-day culture.