Guidelines on the histopathology of chronic pancreatitis. Recommendations from the working group for the international consensus guidelines for chronic pancreatitis in collaboration with the International Association of Pancreatology, the American Pancreatic Association, the Japan Pancreas Society, and the European Pancreatic Club

Chronic pancreatitis is a complex multifactorial fibro-inflammatory disease. Consensus guidelines are needed for the histopathological evaluation of non-autoimmune chronic pancreatitis (CP).An international working group with experts on the histopathology of CP evaluated 15 statements generated from evidence on seven key clinically relevant questions. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to evaluate the level of evidence available for each statement. To determine the level of agreement, the working group voted on the statements for strength of agreement, using a nine-point Likert scale, and Cronbach's alpha reliability coefficients were calculated.Strong consensus was obtained for 12 statements relating to all seven key questions including that: the cardinal features of CP are the triad of fibrosis, loss of acinar tissue and duct changes; there are no unique histopathological features that distinguish the different aetiologies of CP; clinical history and laboratory investigations, including genetic testing, are important in establishing the aetiology of CP; there is no reproducible and universally accepted histological grading system for assessing severity of CP, although classification as "mild", "moderate" and "severe" is usually applied; scoring systems for fibrosis are not validated for clinical use; asymptomatic fibrosis is a common finding associated with ageing, and not necessarily evidence of CP; there are no obvious diagnostic macroscopic features of early CP; histopathology is not the gold standard for the diagnosis of CP; and cytology alone is not a reliable method for the diagnosis of CP.Cardinal histopathological features of CP are well-defined and internationally accepted and pathological assessment is relevant for the purpose of differential diagnosis with other pancreatic diseases, especially cancer. However, a reliable diagnosis of CP requires integration of clinical, laboratory and imaging features and cannot be made by histology alone.