FISH analysis reveals frequent co-occurrence of 4q24/TET2 and 5q and/or 7q deletions

We investigated TET2 deletion in 418 patients with hematological malignancies. Overall interphase FISH detected complete or partial TET2 monoallelic deletion (TET2del) in 20/418 cases (4.7%). TET2del was very rare in lymphoid malignancies (1/242 cases; 0.4%). Among 19 positive myeloid malignancies TET2del was associated with a 4q24 karyotypic abnormality in 18 cases. In AML, TET2del occurred in CD34-positive hematopoietic precursors and preceded established genomic abnormalities, such as 5q− and −7/7q−, which were the most frequent associated changes (Fisher's exact test P = 0.000).