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Deep learning (DL) has become a remarkably powerful tool for image processing recently. However, the usefulness of DL in positron emission tomography (PET)/computed tomography (CT) for breast cancer (BC) has been insufficiently studied. This study investigated whether a DL model using images with multiple degrees of PET maximum-intensity projection (MIP) images contributes to increase diagnostic accuracy for PET/CT image classification in BC. We retrospectively gathered 400 images of 200 BC and 200 non-BC patients for training data. For each image, we obtained PET MIP images with four different degrees (0°, 30°, 60°, 90°) and made two DL models using Xception. One DL model diagnosed BC with only 0-degree MIP and the other used four different degrees. After training phases, our DL models analyzed test data including 50 BC and 50 non-BC patients. Five radiologists interpreted these test data. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated. Our 4-degree model, 0-degree model, and radiologists had a sensitivity of 96%, 82%, and 80–98% and a specificity of 80%, 88%, and 76–92%, respectively. Our 4-degree model had equal or better diagnostic performance compared with that of the radiologists (AUC = 0.936 and 0.872–0.967, p = 0.036–0.405). A DL model similar to our 4-degree model may lead to help radiologists in their diagnostic work in the future.

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Xanthogranulomatous pancreatitis (XGP) is extremely rare, with only 31 cases reported in the English literature to date. We reviewed previously reported 17 articles about XGP and report an additional case of XGP. This is the first case of XGP with xanthogranulomatous cholecystitis accompanied by intraductal papillary mucinous carcinoma (IPMC) in an 80-year-old woman. She was referred to our hospital with jaundice and general malaise and was found to have a cystic mass at the pancreatic head and a solid mass at the pancreatic tail, with dilation of both the main pancreatic duct and biliary tract noted on computed tomography. Diagnosis of IPMC at the pancreatic head with neuroendocrine tumor at the pancreatic tail was made, and the patient underwent subtotal stomach-preserving pancreatoduodenectomy with enucleation of the mass at the tail. Pathological examination revealed IPMC with xanthogranulomatous changes around the IPMC and at the pancreatic tail and gallbladder. Xanthogranulomatous pancreatitis could be induced by inflammatory reaction due to obstruction of the pancreatic duct and biliary tract by mucin produced in the IPMC. It is sometimes difficult to preoperatively differentiate XGP from malignant pancreatic tumors, such as pancreatic carcinoma or neuroendocrine tumor, using imaging studies.