In conclusion, we propose a new, useful and effective software tool to define circular and linear fusion transcripts in cancer cells with rearranged genomes, and with our case study, we provide new data about f-circRNA expression in BCP-ALL with KMT2A::AFF1 rearrangements and highlight new aberrant transcripts that can be searched for in other possibly larger patient cohorts. Here, AFF1 is linked to acute lymphoblastic leukemia.