Why Should FISH Be Done in Patients with Acute Leukemias to Detect MLL Translocation? / 대한임상병리학회지

ABSTRACT

BACKGROUND: Translocations involving the MLL gene on the long arm of chromosome 11 (11q23) are frequently observed in acute leukemia. The detection of this genetic change has a unique significance due to its implication for poor prognosis. The aim of this study was to determine the utility of fluorescence in situ hybridization (FISH) method in detecting the MLL translocation. METHODS: We applied both conventional cytogenetic analysis (CC) and MLL FISH on 289 consecutive Korean patients (children and adults) with acute leukemia and analyzed the data, placing an emphasis on the discrepancies in the results. RESULTS: Twenty-two of 289 patients (7.6%) had the 11q23/MLL translocation. In 9 cases of 22 (41%), only FISH detected the translocation. In 8 among 22 patients, a total of 19 follow-up examinations were performed, of which FISH detected a significant level of leukemia cells harboring the MLL translocation in 5 (26%) without cytogenetic evidence. Besides the MLL translocation, FISH detected submicroscopic amplification, partial deletion of the MLL gene, and trisomy 11 in 12 cases without cytogenetic evidence. CONCLUSIONS: These results demonstrate that up to 41% of the MLL translocations at initial workups and 26% during follow-up were detected by FISH without cytogenetic evidence. Thus, we recommend that MLL FISH should be performed in the diagnosis and monitoring of acute leukemia in combination with CC.