Myeloid sarcomas are tumour masses of myeloid leukaemic cells at extramedullary sites. These tumours can, on occasion, occur without concurrent or antecedent leukaemia. Myeloid sarcomas have been described at unusual locations including the female genital tract. An unusual case of therapy-related acute myeloid leukaemia (t-AML) presenting as isolated monoblastic myeloid sarcoma of the uterus in a patient who had received adjuvant chemotherapy for breast cancer is presented. Fluorescence in situ hybridisation analysis performed on paraffin-wax-embedded tumour tissue revealed amixed-lineage leukaemia (MLL)gene rearrangement, supporting the association of this malignancy with prior chemotherapy. This case illustrates that t-AML can rarely present as isolated extramedullary tumours, and the detection of specific chromosomal abnormalities in these myeloid sarcomas can be useful for risk assessment and guiding definitive therapy.