Follicular pancreatitis, report of a case clinically mimicking pancreatic cancer and literature review.

We herein present a 71-year-old man who underwent pancreatoduodenectomy with the diagnosis of follicular pancreatitis. We could not completely deny malignancy by a preoperative imaging study. Endoscopic ultrasonography-guided fine needle aspiration biopsy demonstrated clusters of benign acinar cells and no proliferation of atypical lymphoid cells or rich plasma cells. Histologically, the prominent lymphoid follicle formation was seen in an ill-defined mass, 15 mm in size, in the pancreatic parenchyma. Duct-centered fibrotic rims were seen in the pancreatic ducts accompanied by mild fibrotic change between the follicles and obliterative phlebitis. No neoplastic epithelial cells were observed in the resected specimen, and infiltrating lymphocytes did not show any morphological atypia and monoclonal proliferation by immunohistochemical staining with B and T cell markers. In addition, we could exclude IgG4-related disease, because plasmacytic cells were rarely positive for IgG4. Although follicular pancreatitis is rare, this mass-forming inflammatory disease (pancreatitis) should be included in the preoperative differential diagnosis of pancreatic cancer.