Cytogenetic evidence for clonal evolution in B-cell chronic lymphocytic leukemia.

Sequential cytogenetic studies were performed in eight of ten patients with B-cell chronic lymphocytic leukemia presenting with trisomy 12 as the sole chromosomal abnormality. Follow-up studies of peripheral blood lymphocytes revealed that the karyotypes retained the sole abnormality of trisomy 12 in five cases, trisomy 12 converted to a normal karyotype during remission in one case, additional chromosome changes (-X,14q-) along with trisomy 12 appeared in one patient and multiple chromosome changes with or without trisomy 12 appeared in the remaining patient. The findings indicate that other chromosome changes in addition to trisomy 12 may develop as a result of clonal evolution or dedifferentiation, though the possibility that in two patients these changes may be related to chemotherapy and/or irradiation could not be ruled out entirely.