FDG PET/CT and MRI of IgG4-Related Disease Presenting as a Hepatic Solitary Solid Mass

Abstract A hepatic solitary solid mass mimicking malignancy was discovered through MRI and FDG PET/CT in a 76-year-old woman with abdominal pain and no abnormal tumor markers in the blood. She underwent surgery to remove the lesion. Histopathology with biopsy was highly suspicious for IgG4-related disease, although immunohistochemical staining demonstrated non–IgG4-positive plasma cells. Finally, intrahepatic IgG4-related disease was supported by elevated serum IgG4 of 141 mg/dL. IgG4-related disease could manifest as hepatic solitary solid mass without any other organ involvement, and the immunohistochemical staining of IgG4 may be negative.