Pre- and post-therapy 18F-FDG PET/CT of a patient affected by non-HIV multicentric IgG4-related Castleman disease

TO THE EDITOR: Multicentric Castleman disease (MCD) is usually a progressive systemic disease that has a worse prognosis than the unicentric form. The treatment of MCD is based on systemic therapies, such as chemotherapy and monoclonal antibodies. Imaging procedures play an important role in defining the response to treatment. However, no radiologic linchpins exist, due to the lack of evidence. Castleman disease (CD) is a rare lymphoproliferative disorder first described by Benjamin Castleman, a pathologist at the Massachusetts General Hospital. CD may be unicentric or multicentric. Unicentric CD (UCD), the most common form, is localized and may often be successfully treated with local therapies. MCD is a systemic disease, occurs most commonly in the setting of human immunodeficiency virus (HIV) infection, is usually progressive, and has a worse prognosis. The management of MCD may be carried out by systemic therapies. In the past, the diagnostic imaging of CD has largely been supported by conventional structural imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), as well as by traditional nuclear medicine examinations, such as Gallium scan. In the past two decades, F-fluorodeoxyglucose (F-FDG) positron emission tomography (PET/CT) has become an established imaging tool in oncology. In addition, PET/CT has been generating increasing interest in the areas of infectious diseases [1] and fever of unknown origin [2], as well as with lymphoproliferative disorders such as CD [3, 4] particularly in individuals with HIV infection [5]. Here, we present the case of a patient affected by MCD who underwent PET/CT for staging and restaging of the disease. In the diagnostic setting, PET/CT contributed to the identification of the most appropriate node to select for biopsy, whereas it provided objective information regarding the early response to therapy during the restaging.