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Objectives This study aimed to evaluate the pathological features and imaging findings of pancreatic carcinoma in situ (PCIS). Methods Twenty patients with PCIS were categorized as flat (F) (n = 6) and low papillary (LP) (n = 14) types. Results None of F type and 8 (57%) of 14 with LP type lesions showed intraductal infiltrations of the main pancreatic duct (MPD) greater than 10 mm. None of F type and 3 (21%) of 14 with LP type lesions showed skip lesions in the MPD. Magnetic resonance cholangiopancreatography showed irregular MPD stenoses in 5 (83%) of 6 with F and 13 (100%) of 13 with LP type lesions. Magnetic resonance cholangiopancreatography determined that the median lengths of the irregular MPD stenoses were 3.6 mm for F, and 11.6 mm for LP type lesions. Endoscopic retrograde cholangiopancreatography determined that the median lengths of the irregular MPD stenoses were 2.8 mm for F, and 14.3 mm for LP type lesions. Pancreatic cancer recurrences limited to the remnant pancreas occurred in 2 patients with LP type lesions. Conclusions In LP type PCIS, intraductal infiltration of the MPD occurs frequently. There may be multiple lesions, and lesions may recur in the remnant pancreas. Long-term strict follow-up assessments should be implemented for LP type PCIS.

Objectives This study aimed to investigate the utility of fluorodeoxyglucose (FDG) positron emission tomography for solid pseudopapillary neoplasm (SPN) diagnosis. Methods The subjects included 53 cases of SPN. We compared the maximal standardized uptake volume (SUVmax) with those of 25 cases of pancreatic duct cancer and 18 cases of pancreatic neuroendocrine neoplasm. In addition, immunopathological testing for SPN with regard to FDG uptake was undertaken. Results An increase in SUVmax was observed in all tumors with increased tumor diameter. Among tumors of 20 mm or smaller, the SUVmax of SPN was significantly higher than those of pancreatic duct cancer and pancreatic neuroendocrine neoplasm. The results of a pathological study of FDG uptake in SPN revealed increased glucose transporter protein type 1 expression with tumor enlargement. Furthermore, increased hypoxia-inducible factor-1 and vascular endothelial growth factor expression under hypoxic conditions were observed in the areas of necrosis. Conclusions In cases in which high FDG uptake is observed in small pancreatic tumors, FDG positron emission tomography is potentially useful for SPN differentiation. The factors involved in FDG uptake in SPN include cell density and glucose transporter protein expression, as well as hypoxia-inducible factor and vascular endothelia growth factor expression in the hypoxic environment of necrotic areas.