Isolated extramedullary relapse with involvement of the breasts by acute myeloid leukemia (AML) after allogeneic stem cell transplantation is an uncommon event. We here report the case of a 27-year-old female patient, who was diagnosed with high-risk AML (FAB M5, complex karyotype). Fourteen months after successful bone marrow transplantation, she presented with asymptomatic masses in both breasts. Ultrasound-guided biopsy was performed and histopathology revealed relapsing AML. F-18 FDG PET/CT was performed for whole-body staging and intense multifocal uptake was seen in both breasts and in the abdomen. Isolated extramedullary disease recurrence was confirmed by bone marrow biopsy.