18F-FDG PET/CT in the Evaluation of Solitary Extramedullary Plasmacytoma: A Case Series

The role of fluorine-18-fluorodeoxyglucose positron emission tomography/ computed tomography (18F-FDG PET/CT) in patients with multiple myeloma (MM) and other plasma cell disorders is well-known. Solitary plasmacytoma (SP), an extremely rare form within this entity accounting for approximately 4% of plasma cell malignancies, can be classified as solitary bone plasmacytoma (SBP) or solitary extramedullary plasmacytoma (SEMP). Extramedullary plasmacytoma (EMP) is a rare neoplasm characterized by the monoclonal proliferation of plasma cells outside the bone marrow. Breast and craniocerebral regions are the uncommon sites of the presentations of EMP, rarely reported in the literature. The most frequent site of presentation is the upper airways. The EMPs have similar pathogenesis as MM; however, they differ in management as they are radiosensitive in nature, and radiotherapy is the preferred treatment modality. As SEMP has a better prognosis than SPB with a lower conversion rate to MM, accurate staging is essential to plan for the treatment. The 18F-FDG PET/CT has higher sensitivity for the evaluation of treatment response. In the present case series, it was aimed to depict the role of 18F-FDG PET/CT in newly diagnosed SEMP with different sites of origin to exclude further lesions leading to changes in the treatment plan and treatment response assessment.