Cytogenetic studies of the spleen in chronic granulocytic leukaemia

Using a technique of short-term in vitro culture, cytogenetic studies were performed on splenic tissue from 12 patients with chronic granulocytic leukaemia. In eight patients the disease was in its chronic phase and had been treated with busulphan (seven cases) or splenic irradiation (one case). In five of these patients, small numbers of dividing cells possessing the Philadelphia (Ph1) chromosome were observed; in one, only Ph1 -negative metaphases, presumably those of lymphocytes, occurred, and in two patients no dividing cells were obtained. In four patients chronic granulocytic leukaemia had undergone metamorphosis to an acute phase: in two of these patients no dividing cells were observed in splenic cultures with or without added phytohaemagglutinin: this result may have been attributable to prior cytotoxic therapy. In cultures from the other two patients in metamorphosis, almost all dividing cells were Ph1 -positve and many cells possessed two Ph1 chromosomes. Full cytogenetic analysis in one of these cases showed that the spleen contained several closely related cell lines, apparently reflecting progressive tumour cell evolution.