FLT3 mutations at diagnosis and relapse in acute myeloid leukemia: cytogenetic and pathologic correlations, including cuplike blast morphology.
BACKGROUND
Acquired mutations in the fms-like tyrosine kinase 3 gene (FLT3) adversely impact relapse risk after chemotherapy in patients with acute myeloid leukemia (AML). The FLT3 mutation status may differ at diagnosis and relapse, suggesting a potential role in chemoresistance, yet few reports have addressed the cytogenetic and pathologic correlates of FLT3 mutations in relapsed AML.


OBJECTIVE
To determine FLT3 mutations at diagnosis and relapse in a cohort of adult patients with chemoresistant AML and to correlate mutation status with multiple variables.


METHODS
We retrospectively determined FLT3 internal tandem duplication (FLT3/ITD) and FLT3 tyrosine kinase domain mutations in 50 diagnosis/relapse pairs. We correlated FLT3 status with karyotype, World Health Organization 2008 subtype, white blood cell count, biopsy cellularity, blast percentage, and the presence of invaginated ("cuplike") blast nuclei.


RESULTS
In 11 of 50 patients (22%) the FLT3 mutation status differed at relapse and diagnosis, with a trend toward gain of FLT3/ITD (n = 7) and loss of FLT3 tyrosine kinase domain (n = 5) mutations. FLT3-mutated AMLs correlated with the World Health Organization 2008 subtype, AML, not otherwise specified, hyperproliferative features at diagnosis and relapse, and cytogenetic evolution. FLT3-wild type AMLs correlated with the subtype AML with myelodysplasia-related changes and frequently had adverse presentation karyotypes. Cuplike blast morphology was associated with FLT3/ITD+ status and with high mutation levels. Four of 7 patients with relapse-only FLT3/ITD mutations exhibited cuplike blasts at relapse after being noncuplike at diagnosis.


CONCLUSIONS
In addition to well-known correlates in pretreatment specimens, FLT3 mutation status has pathologic and cytogenetic significance at relapse. A shift to cuplike blast morphology at relapse may herald emergence of a previously undetected FLT3/ITD mutation.
McCormick
Stanley R
SR
Department of Pathology, United Hospital, St Paul, MN 55102, USA. stan.mccormick@allina.com
McCormick
Matthew J
MJ
Grutkoski
Patricia S
PS
Ducker
Gregory S
GS
Banerji
Nilanjana
N
Higgins
Rodney R
RR
Mendiola
John R
JR
Reinartz
John J
JJ
D000368:Aged; D002467:Cell Nucleus / Q000235:genetics / Q000473:pathology; D005260:Female; D020440:Gene Duplication; D006801:Humans; D007621:Karyotyping; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics*
C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3