Splenic Epidermoid Cyst arising within an Intrapancreatic Accessory Spleen Masquerading as a Pancreatic Mucinous Cystic Neoplasm-a diagnostic enigma

Abstract Introduction/Objective Accessory spleens are congenital embryological aberrations usually found within the splenic hilum with no clinical significance. An IntraPancreatic Accessory Spleen (IPAS) is an uncommon benign pancreatic lesion encountered clinically. A splenic epidermoid cyst arising within an IPAS is exceedingly rare and is discussed below. Methods/Case Report A 68-year-old male presented with intermittent post-prandial epigastric pain radiating to the left flank for >1.5 years. Radiological imaging identified a 5.2 cm calcified cyst in the pancreatic tail with a differential of mucinous pancreatic neoplasm/ pancreatic pseudocyst. Additionally, a 2.8cm lobulated solid hypoechoic mass was seen at the porta hepatis with a differential of enlarged lymph node/benign neoplasm. Laboratory biochemical tests were within normal limits except for mildly elevated ferritin. Fine needle aspiration biopsy was indeterminate. The patient elected to proceed with surgical resection. A laparoscopic distal pancreatectomy with splenectomy and excision of the hilar mass was performed. The hilar mass was analyzed by hematopathology and revealed a hyaline- vascular variant of Castleman disease. On gross examination of the distal pancreatic/splenectomy specimen, a well- demarcated cystic lesion with brownish fluid was noted within the pancreatic tail. Microscopic examination revealed a nonpathological pancreas separated by a fibrous capsule with a large cyst arising within an intrapancreatic accessory spleen. The cyst was lined with multilayered non-keratinized CK5/6, and p63 positive squamous epithelium with no lymphocytic infiltrates and absent hair/ dermal appendages confirming a splenic epidermoid cyst. Post-operative follow-up at 6 weeks was uneventful. Results (if a Case Study enter NA) NA Conclusion An epidermoid cyst arising within an intrapancreatic accessory spleen (ECIAS) is extremely rare thus precluding accurate preoperative diagnosis as this entity shares similar radiological imaging characteristics as other cystic lesions such as mucinous pancreatic cysts. It is important for anatomic pathologists to recognize and consider the intrapancreatic compartment as a possible location for accessory spleens. Accurate preoperative diagnosis can prevent unnecessary surveillance and/or extensive surgical resection.