A CRLF2 Rearrangement in a Pediatric Patient with B-ALL Detected by FISH Within the Context of a Complex Abnormal Karyotype.

Objectives: B-cell acute lymphoblastic leukemia (B-ALL) is one of the prevalent pediatric leukemias, accounting for 26% of cancers diagnosed in children 0-14 years of age. We present a case report of an 11-year-old girl with B-ALL. The patient was in complete remission nine months after diagnosis but passed away a month later from chemotherapy-induced hepatic failure, renal failure, and febrile neutropenia. Conventional cytogenetics showed a karyotype of 46,XX,del(5)(q31q35),add(6)(q23),del(7)(q32q36),add(11)(q23),ider(21)(q10)add(21) (q22),inc[20]. DNA FISH analysis performed on the bone marrow showed variant rearrangement of CRLF2, as well as loss of ETV6 signals and gain of RUNX1 signals. The presence of CRLF2 rearrangements within the context of a complex karyotype is often associated with CRLF2 overexpression and poor prognosis. The heterogeneity of B-ALL and the variability in the outcomes of patients that lack characteristic genetic abnormalities highlight the importance of profiling unusual genetic cases such as this one and continuing research to understand the molecular mechanisms of rarer mutations.