Kodai Kawaji - Department of Radiology, Kagoshima University, Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima, Japan
Seiji Kurata - Department of Radiology, Kurume University School of Medicine, Kurume, Japan
Katsuhisa Matsuo - Department of Pathology, Kurume University School of Medicine, Kurume, Japan
Hiroaki Miyoshi - Department of Pathology, Kurume University School of Medicine, Kurume, Japan
Jun Akiba - Department of Diagnostic Pathology, Kurume University Hospital, Kurume, Japan
Fumihiko Mouri - Division of Hematology and Oncology, Department of Medicine, Kurume University School of Medicine, Japan
Akiko Sumi - Department of Radiology, Kurume University School of Medicine, Kurume, Japan
Kiminori Fujimoto - Department of Radiology, Kurume University School of Medicine, Kurume, Japan
Toshi Abe - Department of Radiology, Kurume University School of Medicine, Kurume, Japan

۱۸F-FDG PET/CT is regarded as a modality utilized for the purpose of lesion localization, staging and assessment of treatment response in patients with lymphoma. However, it is difficult that we diagnose among multifocal lymphoma, IgG۴-related disease (IgG۴-RD), or a combination of both conditions when confronted with multiple sites of ۱۸F-FDG uptake with heightened serum IgG۴ levels.We present a case of a ۷۲-year-old male who was suspected of Sjögren’s syndrome based on symptoms of xerostomia accompanied by swelling of the bilateral upper eyelid and salivary glands. Following a diagnostic biopsy that revealed mucosa-associated lymphoid tissue (MALT) lymphoma as a possible finding, ۱۸F-FDG PET/CT was conducted, which demonstrated multiple sites of ۱۸F-FDG accumulation. While multifocal MALT lymphoma was initially suspected, the coexistence of IgG۴-RD could not be definitively ruled out due to the elevated serum IgG۴ levels. Subsequent histopathological and immunohistochemical examinations confirmed the diagnosis of IgG۴-producing MALT lymphoma. After receiving systemic therapy with rituximab, the swelling of the bilateral upper eyelid and parotid glands resolved upon visual examination, and the serum IgG۴ levels returned to within the normal range in a few months. No new lesions were detected during the subsequent follow-up examinations conducted over a period of ۳ years.

IgG۴-producing MALT lymphoma, IgG۴-related disease, ۱۸F-FDG PET/CT, multiple ۱۸F-FDG uptake, Plasmacytic differentiation