Follicular Pancreatitis: Case Report and Literature Review

Rationale: Follicular pancreatitis is a very rare type of focal chronic pancreatitis and is often mistaken for pancreatic neoplasms. It is histologically characterized by extensive lymphoid follicular formation with reactive germinal centers. Patient concerns: A 50-year-old man was admitted to our hospital with 1-month history of epigastric pain. Contrast-enhanced computed tomography and magnetic resonance imaging revealed a 4.7 cm sized enhancing pancreatic head mass with anterior mesenteric soft tissue infiltration and superior mesenteric vein invasion. Endoscopic ultrasonography revealed an ill-defined hypoechoic mass in the head of the pancreas. Diagnoses: A laparoscopic surgical biopsy was performed. Hematoxylin-eosin staining showed the acini structure destruction within the pancreatic parenchyma and different-sized lymphoid follicles with reactive germinal centers around the duct. Immunohistochemical examination showed that cells were positive for the B-cell marker CD20, T-cell marker CD3, and slightly positive for IgG4. However, cells were negative for the B-cell marker Bcl-2. Follicular pancreatitis was confirmed based on the findings of histology and immunohistochemistry. Interventions: The patient was regularly followed without any specific treatment. Outcomes: Follow-up computed tomography revealed no change in the lesion 1 year after diagnosis. Lessons: To the best of our knowledge, this is the first case of follicular pancreatitis in Korea.