Primary Hepatic Lymphoma Complicated by a Hepatic Inflammatory Pseudotumor and Tumor-Forming Pancreatitis.

BACKGROUND Hepatic inflammatory pseudotumor (IPT) is considered to be benign in biological behavior, and its malignant transformation is extremely rare. There has only been one published case of primary hepatic lymphoma complicated by hepatic IPT. CASE PRESENTATION A 73-year-old man presented with obstructive jaundice and a pancreatic head mass. Histology of the mass revealed chronic pancreatitis with lymphoid follicle formation, leading to a diagnosis of a suspicion of follicular pancreatitis. After a choledochojejunostomy, a hepatic tumor was detected, and a biopsy revealed lymphoplasmacytic infiltration. Immunohistochemistry confirmed the polyclonal nature of lymphoplasma cells, indicative of an IPT. The hepatic tumor disappeared during follow-up, but the patient exhibited a high fever related to tumor recurrence. A biopsy revealed the co-existence of a diffuse large B-cell lymphoma and an IPT. IgG4-related disease was excluded because storiform fibrosis, obliterative phlebitis, and a significant increase in IgG4-immunoreactive cells were absent in all investigated tissues. The tumor completely disappeared after chemotherapy. CONCLUSION Careful observation is necessary in this kind of situation because the presence of a hepatic IPT may represent an increased risk of malignant transformation.