Pitfalls in pancreatic lesion diagnostics: an accessory intrapancreatic spleen

Introduction. Accessory spleen (splenunculus) is one of the most common benign congenital anomalies in humans. The location of splenunculus may vary from perisplenic, greater omental or mesenterial to intraparenchymal (pancreas, stomach, duodenum, etc.). In the latter case, the additional spleen is called ectopic (from the greekektoposdisplaced). Most frequently detection of such splenic lobules occurs accidentally via abdominal ultrasound.Objective: two cases of verified intrapancreatic accessory spleen (IPAS) and main criteria for differential diagnosis with other hypervascular pancreatic lesions.Materials and methods. We present two case reports: a 43-year-old woman with a history of kidney cancer and a healthy 61-year-old man. In both cases, pancreatic neuroendocrine neoplasia (NEN) was initially suspected. Preoperative diagnostics included abdominal ultrasound examination and multiphase dynamic computed tomography (CT) with intravenous bolus nonionic iodine-based contrast agent (native, arterial – 10 sec, venous – 60 sec and delayed – 300 sec after threshold density of 150 HU in the aorta was exceeded). In one case magnetic resonance imaging (MRI) including axial, sagittal and coronal T1and T2-weighted images, diffusion-weighted images and dynamiccontrast-enhanced series with gadolinium chelate was performed. Both patients underwent robotic assisted distal pancreas resection. Morphological examination revealed IPAS.Results. In contrast-enhanced computed tomography IPAS has densitometric parameters similar to the spleen. Generally, magnetic resonance imaging does not differentiate IPAS, NEN and hypervascular metastases, since all three are generally T2-hyperintense and T1-hypointense. Contrast enhancement pattern with gadolinium chelateswas similar to CT-contrast enhancement pattern.Conclusion. Intrapancreatic accessory spleen does not require surgical treatment. Therefore, differential diagnosis between IPAS and neuroendocrine neoplasia, solid pseudopapillary tumor and hypervascular pancreatic metastases is crucial. MRI has an advantage with non-invasive diffusionweighted images (DWI). The apparent diffusion coefficient (ADC) of IPAS will be quantitatively similar to the main spleen while other lesion will demonstrate lower ADC values. Scintigraphy with red blood cells bound with 99mTc utilizes the reticuloendothelial system (RES) in the spleen demonstrating characteristic uptake in the IPASand the main spleen. Ultrasound with color Doppler and contrast enhancement may be a good addition to our armamentarium. One can evaluate the vascular pedicle of the IPAS, as well as contrast agent retention in RES via sonography. We believe the multimodal approach including MRI with DWI/ADC to be the most effective.