With an increasing awareness of autoimmune pancreatitis (AIP), the number of cases diagnosed as AIP has increased in the last decade.1 A prompt and accurate diagnosis of AIP is beneficial for patients because corticosteroids rapidly ameliorate symptoms despite its malignant-looking appearance on imaging modalities.2,3 However, the number of cases miscategorized as AIP has also been increasing. These cases are treated with unnecessary steroids. Therefore, appropriate treatments are often delayed and the opportunity for surgical resection may be missed in cases of pancreatic cancer. The misdiagnosis of these cases is sometimes related to the misinterpretation of pancreatic biopsy findings.

This review briefly revisits the subclassification scheme of AIP and imaging findings. The microscopic features of and practical tips for a biopsy diagnosis of AIP and other inflammatory conditions are discussed.