Background: Mass-Forming Chronic Pancreatitis (MFCP) is rare. Moreover, atypical MFCP is difficult to differentiate from Pancreatic Carcinoma (PC) in clinical manifestations, laboratory, and imaging examinations. Diagnosis could be supported by the pathological findings of focal inflammatory fibrosis without evidence of tumor in the pancreas. Case summary: A 52-year-old man had acute pancreatitis twice over 7 months. Amylase and lipase levels were three times higher than the normal range without any clinical symptoms. At the 6th month, the patient lost 15 kg of weight, and abdominal ultrasonography revealed pancreatic head space occupied. All the findings in multimodal imaging including computed tomography image, Magnetic Resonance (MR) imaging with MR cholangiopancreatography, and 18F-FDG positron emission tomography/computed tomography showed an irregular nodule with low density, low signal, and low echo in the head of the pancreas, which were lower than those in the normal pancreatic tissue. The proximal main pancreatic duct was truncated and stenosed, and the distal duct was dilated. Subsequently, he developed progressive painless jaundice, and the specific tumor marker levels were increased. Most of these manifestations were suggestive of the pancreatic malignant tumor; however, multiple specimen pathological findings obtained from laparotomy and endoscopic ultrasonography-guided fine-needle aspiration revealed focal chronic inflammation, fibrosis, and necrosis. Conclusion: This report describes a case of atypical MFCP mimicking PC at clinical presentation and laboratory findings, especially in multimodal imaging. However, the combination of atypical multimodal imaging features, which support MFCP rather than PC, and endoscopic ultrasonography-guided fine-needle aspiration are useful for improving the diagnostic rate of atypical MFCP and avoiding unnecessary surgery.
Reporting Standards for Chronic Pancreatitis by Using CT, MRI, and MR Cholangiopancreatography: The Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer