The significance of Ph1 mosaicism: a report of six cases of chronic granulocytic leukaemia and two cases of acute myeloid leukaemia.

Six cases of chronic granulocytic leukaemia (CGL) and two cases of acute myeloid leukaemia (AML) with dual populations of karyotypically normal and Philadelphia (Ph1) chromosome-positive cells are described. GTG and QF-banding characterized the Ph1 as resulting from a 9/22 translocation in all eight cases. Four of the patients suffering from CGL presented with 100% Ph1-positive bone marrows, and after receiving intensive chemotherapy, karyotypically normal cells were demonstrated. The other two patients with CGL showed Ph1 mosaicism at presentation. The two patients with AML exhibited Ph1 mosaicism at presentation and throughout the course of the disease. In both of these patients, a marker No. 10 chromosome was found in some of the Ph1-positive cells and in one hyperdiploidy was observed to have developed only in the clone with the additional chromosome anomaly.