IgG4-Related Pseudotumors Mimicking Metastases in Liver and Lungs

A 47-year-old man complained intermittent dull pain at the right upper quadrant abdomen and right neck swelling for 3 months. Blood tests revealed leukocytosis with mild eosinophilia. Computed tomography (CT) showed the presence of multiple nodules in the liver and both lung fields. Positron emission tomography/CT (PET/CT) scans found increased uptake at lymph nodes of the right neck, in the lung, liver, and prostate. The patient was diagnosed with IgG4-related disease (IgG4-RD) based on the biopsy findings from the right neck lymph nodes, showing enriched IgG4-positive lymphoplasmacytic cells. It is often difficult to distinguish IgG4-RD from malignancy, especially in presentations with multiple pseudotumors. This case serves as a reminder that IgG4-RD should be considered in earlier diagnosis, since pseudotumors in multiple organs may imitate tumor metastases.