[Acute promyelocytic leukemia and 15;17 chromosome translocation]

Cytogenetic studies using Giemsa R-bands after a short term culture of bone marrow or peripheral blood were done in 20 cases of acute promyelocytic leukemia (APL), including three cases of microgranular variant. As a result, t (15;17) cells were found in all the cells, and the percentages of the abnormal cells were 38-100%. In 2 cases, t(15;17) was seen in 88% and 65% of the cells in cultured specimens, whereas no such translocation was seen in direct specimens. Among 6 cases treated with tretinoin, 5 achieved complete remission, and among 14 cases treated by HOAP protocol 2 achieved complete remission. Reexamination of 4 of these cases during the stage of complete remission failed to find t(15;17). These data revealed that t(15;17) may probably be present in all cases of APL, and therefore is a very useful diagnostic criterion, especially in cases of micro granular APL. But the detection rate is determined by methodology, which requires special precaution.