Transformation in chronic granulocytic leukaemia. Different blast cell clones in different anatomical sites.

A 45-year-old female developed blastic metamorphosis in chronic granulocytic leukaemia after 52 months of chronic phase. During the subsequent 6--7 months, lymphosarcomatous enlargements of various lymph nodes developed. The blast cells in lymph nodes differed morphologically from those in bone marrow and blood, being 'lymphoid' non-B, non-T, non-ALL cells. The karyotype of all metaphases from one lymph node was 47,XX, +21(Ph1+) being identical to the karyotype of medullary cells. However, the karyotype of all blasts from another lymph node was 47,XX,+mar(Ph1+). It is likely that the local micro-environment controlled the clonal differentiation of these subpopulations which had originated from the same Ph1-positive multipotent stem cell. In lymph nodes and other extramedullary sites blasts were primitive without differentiation, but a myeloid differentiation in the bone marrow was demonstrated morphologically and cytochemically.