Pancreatic nodule positive for 68-Ga-DOTAPEPTIDE-PET: NET or ectopic spleen? The importance of a good differential diagnosis

Accessory spleen is a congenital defect in which splenic tissue is present outside the spleen. In 20% of cases, accessory spleen is localized within the pancreatic tail, a condition known as IPAS. The identification of this benign anomaly, which affects about 2% of general population, is not easy because it is often mistaken for a pNET which is more common, at around 5%. A 68-Ga-DOTAPEPTIDE-PET normally identifies pNETs with high rate of sensitivity and specificity, but in some conditions, it produces false positives, including IPAS. A clinical case we recently encountered, prompted us to review the available medical literature on the topic. Typing “intrapancreatic accessory spleen” into PubMed database and limiting research to the last 10 years yielded 121 results from which we selected the most relevant articles for decision-making, with a brief explanation of the reasons for selecting those. Our analysis focused on the most critical and least descriptive articles, those which clearly indicated the importance of differential diagnosis by promoting the use of advanced investigations in case of pancreatic nodule suspected for IPAS. Ultimately, our objective was to update the available guidelines recommendations. Despite concern in the medical literature, a differential IPAS diagnosis is still subordinate to other clinical, radiological, nuclear medicine, and cytological criteria. After reviewing the literature, we recommend that IPAS should always be considered as a possibility before diagnosis of pNET is made. IPAS should be suspected in the presence of the following findings: asymptomatic pancreatic nodule found incidentally, absence of laboratory findings of NETs, localization in the pancreatic tail, between 1 and 3 cm in size with well-defined margins, homogeneous enhancement, and similar attenuation to the spleen on CT and MRI. In these cases, the use of advanced investigations beyond 68-Ga-DOTAPEPTIDE-PET must be systematic. The recognition of IPAS is not only a diagnostic refinement, but it also avoids unnecessary surgery for the patient.