CRLF2-positive B-cell acute lymphoblastic leukemia in adult patients: A single-institution experience

Objectives: Cytokine receptor-like factor 2 (CRLF2) rearrangement is found in approximately 50% of pediatric Ph-like B-cell acute lymphoblastic leukemia (B-ALL), and around 50% of CRLF2-cases harbor JAK mutations. We analyzed CRLF2 expression and studied its correlation with CRLF2 rearrangement in adult patients with B-ALL. Methods: Multiparameter flow cytometry (MFC) was performed consecutively in 126 patients. Results: CRLF2 overexpression was detected in 30 (27%) patients, 28 (41%) of 69 patients with B-ALL not otherwise specified, 14 (21%) of 67 untreated patients, and 16 (27%) of 59 patients with relapsed B-ALL, with the highest among Hispanic patients (25/55, 45%). Of CRLF2-cases, 21 (100%) of 21 cases showed CRLF2 rearrangement by fluorescence in situ hybridization, preferentially involving IGH@CRLF2 (15/15). The entire coding region of JAK2 was sequenced in 14 patients with CRLF2pB-ALL, and nine (64%) were positive for JAK2 mutations. Conclusions: MFC allows a rapid, inexpensive, and reliable detection of B-ALL with CRLF2 rearrangement that would further facilitate testing for JAK2 mutations for targetable therapy.