Postoperative Hepatic Inflammatory Pseudotumor in Autoimmune Pancreatitis: Hepatic Involvement of IgG4-related Disease

Autoimmune pancreatitis (AIP) is a rare subtype of chronic pancreatitis with IgG4-positive lymphoplasmacytic infiltration and storiform fibrosis, often mimicking pancreatic cancer.A 69-year-old male presented with abdominal pain, jaundice, elevation of cholestatic enzymes, and elevated CA 19-9.Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography demonstrated diffuse pancreatic enlargement, T1 hypointensity, and delayed enhancement.Malignancy could not be excluded; pancreaticoduodenectomy confirmed Type I IgG4-related AIP.Two months postoperatively, MRI detected a cystic-cavitary hepatic lesion.Infectious causes were excluded, and corticosteroid therapy for presumed hepatic inflammatory pseudotumor (IPT) achieved complete resolution.AIP may closely resemble pancreatic adenocarcinoma clinically and radiologically, particularly in focal disease.Accurate diagnosis requires integrated evaluation of MRI morphology, ductal configuration, and enhancement behavior.Although uncommon, hepatic IPT is a key extrapancreatic manifestation of IgG4-related disease and should be recognized as a benign, steroid-responsive entity to avoid unnecessary surgical intervention.