Introduction
ZNF384 (zinc finger protein 384) re-arrangements are recently recognized cytogenetic abnormalities that occur in as many as 48% of mixed-phenotype acute leukaemia (MPAL), B/myeloid and 4% of B-cell precursor acute lymphoblastic leukaemia (BCP-ALL)1. Several fusion partners of ZNF384 have been described, the most common being TCF3, but also EP300, ESWR1, TAF15, CREBBP, ARID1B, SYNRG and BMP2K 1–3 We report a challenging case with TCF3-ZNF384 rearrangement that initially presented as BCP-ALL but showed the emergence of a large myeloid blast subset following one week of high-dose steroid therapy.