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From question on page 1372
With an initial diagnosis of pancreatic pseudocyst, transgastric endoscopic ultrasound‐guided drainage of the cystic lesion was performed. Amylase level of drained fluid was extremely high (11370 IU/l), gradually declining to 91 IU/l. Follow‐up computed tomography showed a croissant‐shaped mass adjacent under the cystic lesion (fig 11).). This mass was diagnosed as an accessory spleen on the basis of significant signal decrease as the splenic parenchyma on post‐contrast T2‐weighted image of superparamagnetic iron oxide‐enhanced magnetic resonance imaging (fig 22 pre‐contrast, fig 33 post‐contrast). Distal pancreatectomy and splenectomy were performed. The cyst was surrounded by the accessory spleen (6.0×5.0×1.0 cm in size) and adhered to the pancreas. Pathological examination showed that the cyst wall was lined with stratified squamous epithelium, suggesting a diagnosis of an epidermoid cyst.
Epidermoid cysts arising from an accessory spleen in the pancreas are rare. To date, fewer than 20 cases have been reported since 1980.1,2 Their median size is 3.5 cm (range, 1.5–15 cm). Patients with large cysts have abdominal discomfort due to compression. It is hard to make a preoperative definite diagnosis of epidermoid cysts in an intrapancreatic accessory spleen. They might be misdiagnosed as pancreatic cystic tumours or pancreatic pseudocysts. Actually, we initially diagnosed the cyst as a pancreatic pseudocyst based on endoscopic retrograde pancreatography findings which revealed communication between the pancreatic duct and the cyst. Such a communication is unusual with a pancreatogram of epidermoid cysts arising from the intrapancreatic accessory spleen.1,2 Although the pathogenesis of this communication is unknown, we consider that the cystic lesion in the present case was the largest one among the reported series because of the inflow of pancreatic juice into the cyst.
The accessory spleen surrounding the cyst is a clue for a preoperative diagnosis. Although an accessory spleen can be suspected by its simultaneous enhancement with the spleen in early‐phase dynamic computed tomography,3 marked signal decrease by superparamagnetic iron oxide, and negative enhancement material uptaken by reticulo‐endotherial cells, is essential to confirm the diagnosis of the accessory spleen in magnetic resonance imaging. In patients with cystic lesions around the pancreatic tail, an epidermoid cyst originating from an accessory spleen should be considered.