title: Follicular pancreatitis: a distinct form of chronic pancreatitis-an additional mimic of pancreatic neoplasms.
abstract: Follicular pancreatitis is a recently described variant of chronic pancreatitis characterized clinically by the formation of a discrete pancreatic mass and histologically by the presence of florid lymphoid aggregates with reactive germinal centers. Our aim was to study the clinical and histologic features of follicular pancreatitis, as well as to critically examine potential overlap with autoimmune pancreatitis. Immunohistochemistry for Bcl-2, CD21, κ and λ light chains as well as IgG4 and IgG were performed. We found a total of 6 patients (male-female ratio, 2:1; mean age, 57 years) who fulfilled the diagnosis of follicular pancreatitis in our institutions. Four had an incidental diagnosis, while two presented with abdominal pain, fatigue, and elevated liver enzymes. On imaging, 3 patients had a discrete solid mass, whereas 2 cases showed a dilated main pancreatic duct, mimicking an intraductal pancreatic mucinous neoplasm on imaging. One patient had a lesion in the intra-pancreatic portion of the common bile duct. On histopathology, all cases showed numerous lymphoid follicles with Bcl-2-negative germinal centers either in a periductal or in a more diffuse (periductal and intra-parenchymal) fashion, but without attendant storiform fibrosis, obliterative phlebitis, or granulocytic epithelial lesions. IgG4-to-IgG ratio was <40% in 5 cases. A comparison cohort revealed germinal centers in 25% of type 1 autoimmune pancreatitis and 2% of type 2 autoimmune pancreatitis cases, but none were periductal in location. In conclusion, follicular pancreatitis, an under-recognized mimic of pancreatic neoplasms is characterized by intrapancreatic lymphoid follicles with reactive germinal centers.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Tennessee Health Science Center, Memphis, TN, 38163. Electronic address: rajibgupta2011@gmail.com.
authors.forename: Rajib K
authors.initials: RK
authors.lastname: Gupta
authors.affiliation: Pathology Group of Midsouth (Trumbull Laboratories), Germantown, TN, 38138; Department of Pathology, Baptist Memorial Hospital, Memphis, TN, 38120. Electronic address: hbup@yahoo.com.
authors.forename: Bill H
authors.initials: BH
authors.lastname: Xie
authors.affiliation: Pathology Group of Midsouth (Trumbull Laboratories), Germantown, TN, 38138; Department of Pathology, Baptist Memorial Hospital, Memphis, TN, 38120. Electronic address: kurt_patton@yahoo.com.
authors.forename: Kurt T
authors.initials: KT
authors.lastname: Patton
authors.affiliation: Department of Pathology, Dartmouth-Hitchcock Medical Center and Geisel School of Medicine at Dartmouth, Lebanon, NH. Electronic address: mikhail.lisovsky@hitchcock.org.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Lisovsky
authors.affiliation: Department of Pathology, Lahey Hospital, Burlington, MA, 01805. Electronic address: eric.burks@lahey.org.
authors.forename: Eric
authors.initials: E
authors.lastname: Burks
authors.affiliation: Division of Surgical Oncology, Department of Surgery, University of Tennessee Health Science Center, Memphis, TN, 38163; Department of Surgery, Baptist Memorial Hospital, Memphis, TN, 38120. Electronic address: sbehrman@uthsc.edu.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Behrman
authors.affiliation: Department of Pathology, Memorial Sloan-Kettering Cancer Center and Memorial Hospital for Cancer and Allied Diseases, New York, NY, 10065. Electronic address: klimstrd@mskcc.org.
authors.forename: David
authors.initials: D
authors.lastname: Klimstra
authors.affiliation: Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02114. Electronic address: Vikramdirdeshpande@gmail.com.
authors.forename: Vikram
authors.initials: V
authors.lastname: Deshpande
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D018858:Germinal Center / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis; D050500:Pancreatitis, Chronic / Q000473:pathology*
chemical_list: D015415:Biomarkers
keywords: Autoimmune pancreatitis; Follicular pancreatitis; IgG4; Lymphoma; Pancreatitis