Detection of 16 p deletions by FISH in patients with inv(16) or t(16;16) and acute myeloid leukemia (AML)

Deletions of sequences centromeric to the p-arm breakpoint have been described in a subset of patients with inv(16) and acute myeloid leukemia (AML) and reported to be associated with a relatively good prognosis. We have investigated 16 p deletions in a cohort of 15 patients with AML and inv(16) or t(16;16) and compared non-deletion and deletion patients in terms of clinical course. Patients were studied by fluorescence in situ hybridization (FISH) using cosmid zit14 as a probe to detect the presence of 16 p deletions in metaphase chromosomes of leukemic cells. While seven patients (47%) revealed no evidence of a deletion, five patients (33%) presented 16 p deletions, thus bringing further support to the relatively frequent occurrence of this event in inv(16) patients. Remarkably, two patients with inv(16) and one patient with t(16;16) showed a mosaicism of deletion and non-deletion metaphases suggesting the presence of two distinct leukemic cell populations. Results let us assume that 16 p deletions are not restricted to inv(16) and may occur subsequently to inv(16) or t(16;16). The presence of a 16 p deletion in a case of inv(16) associated with CBFB-MYH11 transcript type E indicates that deletions are not limited to CBFB-MYH11 transcript type A rearrangements. Survival of deletion patients was compared with that of nondeletion and mosaic ones. No significant differences were observed. The advantage of FISH for enumerative and quantitative assessment of submicroscopic rearrangements of clinical significance is further emphasized.