Clinical and imaging differentiation of intrapancreatic accessory spleen from pancreatic neuroendocrine tumor and solid-pseudopapillary tumor: a retrospective analysis

Background Intrapancreatic accessory spleen (IPAS) represents a rare anatomical variant of the spleen that is misdiagnosed as pancreatic neoplastic lesions. Notably, IPAS is often erroneously identified as pancreatic neuroendocrine tumor (PNET) or solid pseudopapillary tumor (SPT), which consequently results in unnecessary resection of the pancreas. This study aimed to summarize the clinical, imaging and laboratory characteristics of these lesions, clarify the key differential diagnostic points among them, and thereby enhance the clinical understanding and preoperative diagnostic accuracy of IPAS. Methods This retrospective study analyzed all 7 cases of IPAS diagnosed at our hospital from January 2008 to December 2025. For comparative analysis, consecutive patients with pathologically confirmed PNET ( n = 18) and SPT ( n = 21) treated at the same institution between January 2023 and June 2025 were included. Clinical, imaging and pathologic characteristics were compared descriptively. Key points of differential diagnosis were summarized. Results IPAS was distinguished from PNET and SPT primarily by consistent location in the pancreatic tail (100%), frequent heterogeneous arterial-phase enhancement with CT attenuation often similar to the spleen, universal adjacency to the splenic vessels, solid consistency, and predominantly reddish-brown gross appearance, with most lesions showing a soft texture. In contrast, PNET and SPT showed more variable location, enhancement patterns, attenuation relative to spleen, vessel contact rates, and pathologic color/texture. SPTs are typically larger and more frequently exhibit calcification. Conclusion For lesions located in the pancreatic tail, adjacent to the spleen, and exhibiting heterogeneous enhancement in the arterial phase, the possibility of IPAS should be thoroughly considered. Nevertheless, surgical resection remains rational and appropriate when preoperative evaluation cannot completely exclude the possibility of PNET, SPT, or other pancreatic lesions.