Mass-forming extramedullary hematopoiesis in multiple myeloma: 18F-FDG PET/CT is useful in excluding extramedullary myeloma involvement

Aims and background: Extramedullary hematopoiesis (EMH), a benign condition, is usually observed in patients with hematologic disorders. We report the first case of mass-forming EMH detected on a 18F-fluoro-2-deoxyD- glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scan in a patient with multiple myeloma (MM). Methods: A 58-year-old woman underwent workup for bicytopenia, and was diagnosed with MM based on the results of bone marrow aspiration and serum protein electrophoresis. An 18F-FDG PET/CT scan revealed a paravertebral mass with mild FDG avidity, suggesting a tumorous condition. Results: Biopsy was performed to exclude malignancy and the mass was eventually confirmed as EMH. Conclusions: Differential diagnosis of a mildly FDG-avid paravertebral mass in MM should include EMH.