Lymphoblastic Leukemia With P2RY8::CRLF2 Rearrangement and High Hyperdiploidy.

Improved survival rate in pediatric acute lymphoblastic leukemia (ALL) warrants efforts to optimize treatment intensity in good-prognostic groups such as those with high hyperdiploidy (HHD). Cytokine receptor-like factor 2 (CRLF2) alteration is frequently detected in Philadelphia chromosome-like ALL, which has a high relapse ratio and no consensus treatment strategy. P2RY8::CRLF2-positive childhood ALL is frequently associated with disease recurrence. To the best of our knowledge, there have been no previous case reports of an ALL patient with P2RY8::CRLF2 fusion gene, CRLF2 high expression, and HHD that have included a detailed description of the clinical course. Here we report the case of a 3.3-year-old Sri Lankan boy diagnosed with B-cell precursor (BCP) ALL with P2RY8::CRLF2, CRLF2 hyperexpression, and HHD. The patient's rapid minimal residual disease (MRD) clearance and HHD karyotype supported classification as standard-risk, per Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Münster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL2000) criteria. However, the contribution of CRLF2 overexpression to long-term risk remains uncertain. At 54 months since diagnosis, he remains in good health following his initial complete response.