18 F-FDG PET/CT imaging of a 68-year-old woman with a known clinical diagnosis of systemic lupus erythematosus and recent-onset ataxia revealed FDG-avid soft tissue masses in bilateral renal sinuses and mildly increased bone marrow activity. Consecutive tissue sampling with fine-needle biopsy from renal sinus masses confirmed mass-forming extramedullary hematopoiesis corresponding to FDG-avid soft tissue lesions. Here we present a rare case of bilateral mass-forming extramedullary hematopoiesis at renal sinuses incidentally detected on 18 F-FDG PET/CT imaging.