Conventional karyotyping and fluorescence in situ hybridization: an effective utilization strategy in diagnostic adult acute myeloid leukemia.

OBJECTIVES

Cytogenetics defines disease entities and predicts prognosis in acute myeloid leukemia (AML). Conventional karyotyping provides a comprehensive view of the genome, while fluorescence in situ hybridization (FISH) detects targeted abnormalities. The aim of this study was to compare the utility of karyotyping and FISH in adult AML.

METHODS

We studied 250 adult AML cases with concurrent karyotyping and FISH testing. Karyotyping was considered adequate when 20 or more metaphases were analyzed.

RESULTS

In total, 220 cases had adequate karyotyping and were classified as normal karyotype/normal FISH (n = 92), normal karyotype/abnormal FISH (n = 4), abnormal karyotype/normal FISH (n = 8), and abnormal karyotype/abnormal FISH (n = 116). The overall karyotype/FISH concordance rate was 97.7% with five discordant cases identified, four from the normal karyotype/abnormal FISH group and one from the abnormal karyotype/abnormal FISH group. No karyotype/FISH discordance was seen in the abnormal karyotype/normal FISH group for the FISH probes evaluated. FISH lent prognostic information in one (0.5%) of 220 cases with normal karyotype/abnormal FISH: CBFB-MYH11 fusion, indicating favorable prognosis.

CONCLUSIONS

In adult AML, FISH rarely provides additional information when karyotyping is adequate. We therefore propose an evidence-based, cost-effective algorithmic approach for routine conventional karyotype and FISH testing in adult AML workup.